Labour MP Ian Gibson announced today that he was resigning with immediate effect - forcing a by-election in his Norwich North constituency.
Dr Gibson said his de-selection as a Labour candidate over his expenses claims had left him "bowed but not broken".
But his position for the rest of the Parliament was now "untenable", he said in a statement.
Earlier this week Dr Gibson was barred by Labour's ruling National Executive Committee from standing as a candidate for the party at the next General Election.
The move followed a "star chamber" inquiry into his expenses claims after allegations that he sold a taxpayer-subsidised flat to his daughter for less than the market value.
Dr Gibson said today that it was still "unclear" to him what expenses rule he had contravened, adding: "The decision of the NEC leaves me today bowed but not broken.
"However, I believe that my position as an MP between now and the next election is untenable.
"And after discussions with my family, colleagues, party members and my admirable staff, I have decided to tender my resignation as an MP with immediate effect and I expect it to be accepted."
By resigning now rather than waiting until the next General Election, Dr Gibson has forgone a pay-off worth tens of thousands of pounds.
Because he has passed his 70th birthday, Dr Gibson would have been entitled to a resettlement grant of half his annual MP's salary, which is currently £64,766.Reuse content