The Conservative MP at the centre of a storm for paying his son almost 50,000 pounds of public money for doing nothing faces a Commons vote on Thursday which is almost certain to suspend him for 10 days.
Derek Conway, 54, who could also face a police investigation, said on Wednesday he will quit politics at the next election.
Conservative leader David Cameron expelled Conway from the parliamentary party on Tuesday.
Conway said he would stand down as he did not want to be a "distraction".
He says his son had been acting as his researcher while at university and that the money had been paid in salary to him.
But the Commons standards committee found his son had done little or no work for him and recommended he be suspended from parliament for 10 days and repay more than 13,000 pounds.
MPs will vote on that recommendation and are widely expected to approve it.
Frederick Conway, 22, a Newcastle University geography student was paid almost 12,000 pounds a year, plus bonuses, for almost three years.
Leaked documents also show Conway's elder son, Henry, 25, had been paid more than 32,000 pounds in parliamentary allowances and bonuses between 2001 and 2004 when he too was an undergraduate.
The Metropolitan Police confirmed it had received a letter from Liberal Democrat Duncan Borrowman, who is contending Conway's seat, asking them to investigate whether fraud had been committed.
On Monday, Conway apologised in the Commons for his "administrative shortcomings and misjudgements".
