A Brexit Party running mate of Nigel Farage in Thursday's European election helped spread fake news for a Bosnian Serb warlord later jailed for crimes against humanity, an investigation by SourceMaterial and openDemocracy has discovered.

John Kennedy, a former Tory now standing in the South East region on a list headed by Farage, was for a time monitored by the security services for his close work with Radovan Karadžić, who in March was sentenced for life on charges including genocide, murder and extermination.

A former equerry to Prince Michael of Kent and one-time owner of the Almanach de Gotha, a directory of Europe's aristocracy, Kennedy in July 1992 organised a Westminster press conference with Karadžić at which they distributed a pamphlet listing Bosnian atrocities against Serbs that were later disproved.

Kennedy was a prominent “influence within parts of the British establishment at the time and drew several MPs from across the political spectrum into his circle,” said Carole Hodge, author of ‘Britain and the Balkans’.

Kennedy said yesterday that his involvement with Karadžić ceased “long before any persons were charged with any crime”.

“I met with Karadžić together with UK MPs and Privy Councillors from all parties, including Paddy Ashdown and others. These meetings were not secret or criticised or commented upon by the media at the time, only some years later when I became a Conservative parliamentary candidate.”

While acknowledging that he may have been “naive”, Kennedy did not comment on whether he knew at the time that the 1992 pamphlet contained falsehoods.

In 1996 the High Court ordered the Labour Party to pay him unspecified damages after it wrongly alleged he had retained links with Karadžić and suggested he was not fit to stand for public office in the UK. The party’s lawyer said it accepted Kennedy had “acted at all times with the best of intentions and motives consistent with the wishes of the international community in making a peaceful solution to the conflict”.

But even after his ties to Karadžić ceased, Kennedy continued to spread baseless rumours about Bosnian atrocities. In a 1997 letter to The Guardian, he repeated claims that Bosnians bombed their own civilians as they queued for bread in a bid to engineer international sympathy – a conspiracy theory promoted by a UN peacekeeper later shown to have accepted payments for speaking engagements from a pro-Serb lobby group.

“The claim that the bread queue massacre was a false flag operation was very quickly widely denounced by many people at the time as propaganda on behalf of the Serb extremists” said Marko Hoare, a Balkan historian.

Kennedy did not respond to detailed questions from SourceMaterial and openDemocracy about his past relationship with Karadzic.

The Brexit Party is riding high in the polls, but the source of the party’s funding is being reviewed by the elections regulator and senior officials have resigned over racist and anti-Semitic social media posts.

Kennedy, seventh on the Brexit Party’s South East list, appeared alongside Farage in Frimley, Surrey, on Sunday night. He accused Theresa May and Jeremy Corbyn of working on a “Fisher Price guide book to treaty making” in their failed negotiations on securing Brexit.

‘Unsubstantiated claims and gross falsehoods’

Born Jovan Gvozdenovic, Kennedy twice stood as a Tory candidate in general elections in the 1990s. Following the outbreak of war in the Balkans, Kennedy emerged as a young and suave advocate for the Serbs in the UK, often briefing journalists and appearing on television news while also deploying high-level connections to win MPs to the Serbian cause.

During the brutal early stages of the war, as Serbian forces opened a campaign of ethnic cleansing, Kennedy helped organise trips to Belgrade for British politicians to meet Slobodan Milošević, the Serbian president who later died in the Hague while on trial for war crimes.

The dossier distributed by Kennedy and Karadžić at the 1992 London press conference denied ethnic cleansing by the Serbs – allegations which were later proven at a tribunal in the Hague. The dossier instead levelled that very charge at rival Bosnian Muslim forces. It contained lurid descriptions of alleged Bosnian crimes, including claims that Bosnians executed Serbs by the “extraction of the brains of living humans”.

It was “propaganda that contains unsubstantiated, fantastical claims and grotesque falsehoods,” said Marko Hoare, a Balkan historian.

Paddy Ashdown, the former leader of the Liberal Democrats who later became de facto governor of Bosnia, recalled Kennedy as a Karadžić confidant and lobbyist who was so well-connected with the warlord that he could rouse him to the telephone “at 2:30am in the morning!”.

“Kennedy in good form, having just come back from Geneva,” Ashdown wrote in diaries published in 2000. “Full of the old bullshit, however,” including a warning that Serbs would shoot down planes and even had “tactical nuclear weapons near Sarajevo”.

“He clearly thinks they have won and has seventy-three different reasons why we should not support the Muslims. A remarkable man. Extraordinary self-confidence but lacking in plain common sense. Somehow, he is good company, even if – or perhaps because – he is so provocative.”

Kennedy said: “These are all events that took place 27 years ago, when I was 27 years of age. This was an appalling and tragic conflict, all of my endeavours were entirely based on the belief that something could be done to shorten that conflict."

Brexit: ‘Nigel’s own private political party’

In a matter of months, Nigel Farage’s Brexit Party has emerged as a major force in British politics. Kennedy is not the only Brexit Party hopeful with a controversial record over the war in the Balkans. Four other candidates – Claire Fox, Alka Sehgal Cuthbert, James Mountfield and Stuart Waiton – were previously involved in the Revolutionary Communist Party or its offshoots such as Living Marxism, Spiked and the Institute of Ideas.

The RCP, an unabashed backer of the IRA, took a strongly pro-Serb line in the Balkan conflict, culminating when Living Marxism magazine accused ITN of broadcasting deliberately misleading footage of Bosnian Serb war crimes. ITN and two journalists won a libel case against the magazine, bankrupting it.

Kennedy said he has no connection with the RCP or Living Marxism and did not know Fox “until a couple of weeks ago”.

Revelations about Brexit Party candidates’ links to Living Marxism and other groups raise questions in particular for Nigel Farage who, according to a party insider, personally oversees the selection of candidates.

“It’s Nigel’s own private political party,” said the insider, who asked not to be identified.

Mixing business and politics

Kennedy began his public relations career working for Ian Greer, a lobbyist whose reputation was destroyed in the ‘cash-for-questions’ scandal in the mid-1990s. After the imposition of sanctions against the Serbs, he struck out on his own, playing a role in facilitating a donation to the Tories by a Serbian-born business partner of Serbia’s foreign minister. The affair prompted an internal Conservative Party investigation which concluded that there was no impropriety.

Kennedy’s influence extended beyond the Tories. David Clark, a Labour minister, and his assistant John Reid – himself later a minister – apologised for not declaring that Kennedy paid for their 1993 trip to Geneva to meet Karadžić.

Kennedy also appears to mix politics with business. In 1993 he founded two companies with Harold Elletson, a pro-Serb Tory MP. Henry Bellingham, who hosted the 1992 Karadžić press conference and for a time employed Kennedy as a researcher, was also a director in a company established by Kennedy.

Bellingham chaired the Conservative Council on Eastern Europe, for whom Greer threw a lavish reception in February 1992 at the National Portrait Gallery, where Milošević supporters mixed with politicians and businessmen, according to The Guardian.

In the late 1990s The Sunday Times, The Observer and The Guardian reported that Kennedy had come into the sights of MI6, who allegedly warned Downing Street that he may be a conduit for Serbian money to the Tory party and obtained warrants to tap his telephones.

“I have not arranged any donation of this kind or from any foreign company or individual,” Kennedy wrote in a letter published by The Guardian in 1997.

Kennedy’s career after his Yugoslav work saw him become a private secretary to Prince Michael of Kent. At one point he was accused of blackmailing a Libyan prince (he has said he was vindicated and no charges were brought).

More recently Kennedy has spoken of capturing the commercial benefits of Brexit in St Lucia, the Caribbean island where his investment fund has been pushing a property development that would take advantage of a citizenship-by-investment scheme.

In July 2016, just days after the European Union referendum, Kennedy wrote that he had briefed the leaders of Saint Lucia’s two main parties about the likelihood of a Brexit vote and called for the country “to be positive in embracing the new opportunities that are already emerging.”