The Turnbull government is considering pursuing dumped senators Bob Day and Rod Culleton to repay hundreds of thousands of dollars to taxpayers.

Senior government figures are discussing whether to go after the pair for up to $250,000 paid to them in parliamentary salaries and expenses last year.

The High Court has now ruled both men were invalidly elected - Mr Culleton because he was bankrupt and Mr Day because he had a constitutionally prohibited financial interest in the Commonwealth because of a complex office leasing arrangement.

Mr Culleton was paid more than $100,000 in salary and superannuation between the July 2 election and the court's decision in January. Mr Day was paid close to $130,000 between February, when the office arrangement took effect, and his November resignation.