David Wildstein, a former Christie appointee who presided over the George Washington Bridge lane closures at the centre of the controversy, said through a letter from his lawyer that "evidence exists . . . tying Mr Christie to having knowledge of the lane closures, during the period when the lanes were closed, contrary to what the Governor stated publicly".

The office of Mr Christie, a possible Republican presidential hopeful, denied the accusation.

Mr Wildstein is the first Christie ally to publicly question the Governor's account, and his claim could further damage Mr Christie as he tries to restore his image amid aggressive investigations by Democratic legislators and a federal prosecutor.

Also on Friday, Bill Stepien, a longtime political adviser to Mr Christie, said he would refuse to testify before the state legislative committee investigating the episode, raising the possibility that more damaging information could emerge.

Mr Wildstein, who attended the same high school as Mr Christie, was appointed by Mr Christie to a position at the Port Authority of New York and New Jersey.

In September, Mr Wildstein and another of Mr Christie's top appointees at the Port Authority ordered the lane closures, causing four days of gridlock in Fort Lee, New Jersey, apparently as retribution against the town's Democratic mayor for not endorsing Mr Christie for re-election. Mr Wildstein resigned in December.

"Mr Wildstein contests the accuracy of various statements that the Governor made about him and he could prove the accuracy of some," wrote his lawyer, Alan Zegas.

Mr Wildstein gave almost no details about what he was asserting was untrue in Mr Christie's accounts. And he said nothing about what the important evidence was or who had it.

In rejecting Mr Wildstein's accusations, a Christie aide said in an email: "Mr. Wildstein's lawyer confirms what the Governor has said all along: he had absolutely no prior knowledge of the lane closures before they happened and whatever Mr Wildstein's motivations were for closing them to begin with."

Mr Christie said last month he had only recently learnt that the closures had been ordered by his administration.

"I had no knowledge of this – of the planning, the execution or anything about it – and that I first found out about it after it was over," Mr Christie said then. Even when he found out about it, he said: "What I was told was that it was a traffic study."

Washington Post