Bob Crow said he donated his salary for the TfL role to charity

Bob Crow is taking the action after Simon Hughes accused him of not attending Transport for London meetings for over a year despite being paid to.

Mr Crow said it was a "damaging slur" and is also taking libel action against the Evening Standard newspaper.

The union leader said he had attended 10 meetings since March 2003.

He added his salary for the role - which he claimed was less than half the �23,000 quoted by Mr Hughes - was donated to the RMT's orphans fund.

The claims were made in a press release by Mr Hughes who said he would remove Mr Crow from the Transport for London (TfL) board and replace him with an official from the Transport and General Workers Union if he wins the mayoral election on 10 June.

The claims were included in an article in the London Evening Standard.

Mr Crow said: "The statement that I have not attended a single TfL meeting since March 2003 is simply untrue."

The claim was later removed from the press release.