Fianna Fail can relax: the party’s founder is in the clear. Leading Irish historians are dismissing a claim made in a new biography that Eamon de Valera was a British spy.

According to John Turi, an American amateur historian, the future taoiseach was “turned” by the British after the Easter Rising in 1916, agreeing to spy for them in return for not being put on trial for his part in the rebellion. Turi claims the Fianna Fail leader’s trip to America in 1919 was his first covert mission for the British. De Valera is accused of destroying the Americans’ positive image of the Irish and scuttling a pro-Ireland senator’s attempt to win a presidential nomination.

The author reckons De Valera’s unstable upbringing and rejection by his mother and uncle, and his dismissal from the priesthood on the grounds of his illegitimacy, made him “a man less than human”. He argues that this gave De Valera a hatred of Ireland and made him susceptible to betraying it. The book ends with a demand for a posthumous trial on charges of treason, treachery and conspiracy to murder.

Several Irish historians and biographers of the former taoiseach have rejected the claims put forward in England’s Greatest Spy, published by Stacey International.

Tim Pat Coogan, author of Long Fellow, Long Shadow, a biography of De Valera and regarded as a harsh critic of the former president, said Turi’s thesis was farcical. Coogan was alarmed at how often his work was cited in the book, and said he hopes nothing he has written was used to substantiate the spy claims.

T Ryle Dwyer, the author of five books on De Valera, said he had never come across evidence of treachery. “I don’t question many of the things Turi says — there are questions about De Valera’s behaviour at the time of the 1916 rising,” Dwyer said.

“His upbringing certainly wasn’t ideal. He was basically abandoned by his mother and had a need to prove himself, and this caused problems. But to say he gave information to the British is mind-boggling.”

Dwyer and Coogan argue that the way that De Valera was treated by successive British prime ministers does not indicate any secret deal. Dwyer added that Winston Churchill believed he was the devil, and pronounced his name “Devil-Eire” to imply it.

Tom Garvin, professor of politics at University College Dublin, said the book sounded like a distorted version of Irish history and rejected its central thesis as “utter nonsense”. He said the suggestion that De Valera was never put on trial after the Rising was rubbish, dismissing Turi’s assertion that a letter written in 1964 by William Wylie, a prosecuting officer, says no hearing took place.

“Wylie did not say anything of the sort. He says exactly the opposite [in his memoir]; that de Valera was condemned,” Garvin said.

The three historians say De Valera escaped execution after the Rising because the British needed to pacify Irish public opinion, and he was not seen as being of particular importance.

Eamon Ó Cuív, his grandson and the community and rural affairs minister, also dismissed the accusation: “The theory is ridiculous and so I have no further comment.”

Turi, a retired US marine married to an Irish woman, said he had expected Irish historians to disagree, but added: “The evidence is so obvious and readily available, it’s amazing to me that Irish writers never came to this conclusion.”

He decided to write the book having set out to research a Michael Collins biography, but soon finding that “every time De Valera popped up, it was a disaster for Ireland”.

The 470-page hardback will have an initial print run of 3,000 copies and go on sale in Ireland and the UK. Publishers plan to release it in America next year.

Charles Powell, the assistant editor of Stacey International, expects the book to sell well. He said the publishers had been slightly concerned by Turi’s theory, but were reassured by his research and referencing.

“We are convinced of the integrity of the work and try to publish books that raise debate and ask questions,” he said.

“A lot of people agree that the decisions de Valera took were counterproductive to the cause he was supposed to be supporting. Whether that was because he was a British spy or because they were just the decisions he made is more difficult to prove.”

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