Tommy Sheridan, who last year won damages over sex allegations, will be part of a panel of speakers at the City Hall lunchtime event.

Also on the platform will be Joe Higgins TD, a leading figure in a battle against a water tax in Dublin in the 1990s.

Mr Sheridan is a member of the Scottish Parliament. He first came to prominence as a leading campaigner against the Thatcher Government's poll tax.

Last year, he won £200,000 in damages from the News of the World newspaper over claims that he had had an affair and visited a swingers' club in Manchester.

The colourful libel trial saw him sack his legal team and and conduct his own defence.

His wife stood by him and appeared by his side every day at the court.

Mr Sheridan last year split from the Scottish Socialist Party. Some of its members had testified in support of the newspaper.

He has since formed a new left-wing party called Solidarity.

Police recently launched inquiries after a bugging device was found in his car.

The News of the World is meanwhile appealing the libel case verdict.

The authorities have announced a perjury probe on evidence given at the trial.