LIBERAL MP Ken Ticehurst, who lost the seat of Dobell in 2007 to Labor's Craig Thomson, plans to sue Mr Thomson for lost earnings, claiming he was robbed of his seat, costing him a lifetime parliamentary pension of $85,000 a year.

Mr Ticehurst, who was outspent by Mr Thomson three dollars to one in the election, said Labor had ''defrauded'' the people of Dobell by allowing Mr Thomson to run.

'Robbed': Ken Ticehurst. Credit:Phil Hearne

A Fair Work Australia investigation has found that Mr Thomson, former head of the Health Services Union, misused union funds to get himself elected to Parliament.

Mr Ticehurst said then treasurer Peter Costello's office had informed him of allegations about Mr Thomson, including his use of prostitutes, before the 2007 election. ''If we knew, Labor must have known,'' Mr Ticehurst said.