Keith Vaz is facing more questions over his conduct
In October Mr Vaz told Elizabeth Filkin, the parliamentary commissioner for standards, about three properties he owned, during her inquiry into his conduct.
Mr Vaz denies misleading anyone and says his declaration was approved by the registrar for members' interests.
Health problems
The controversial minister has been on sick leave since March after coming under intense media pressure over his business interests.
The parliamentary commissioner found him guilty of failing to declare a payment from a local solicitor but cleared him of nine other charges.
No conclusions were reached on another eight because of a lack of evidence.
Asked about the issue at Labour's morning news conference, Prime Minister Tony Blair said he had "no comment" on the allegations.
"These are just another fresh batch of allegations...doesn't matter what Keith responds to or how many time he knocks them down - just another batch appear," he said.
'Extraordinary'
"I find it quite extraordinary that two days [before] the general election when we could be debating issues like schools, jobs, mortgages, the economy, you return to that subject."
But Liberal Democrat peer, Lord Goodhart - who's a member of the Committee on Standards in Public Life - told the BBC he thought the parliamentary commissioner would want to take a fresh look at Mr Vaz's affairs.
Failure to tell the full truth to the commissioner would be regarded as a very serious matter, he said.
'Intolerable'
Shadow foreign secretary Francis Maude said it was "intolerable" that Mr Vaz was seeking re-election under these circumstances.
And he challenged him to come forward and answer questions on the new allegations.
"What is Tony Blair now going to do about this? Is he going to accept that it's alright for a Labour candidate to apparently tell a deliberate lie to the authorities?" asked Mr Maude.
He went on: "This business about transferring the property between the request for information and the giving of information, that's the way a fly-by-night fraudster might operate - always trying to stay one step ahead of the authorities."
Proper channels
Labour cabinet minister Margaret Beckett has described Mr Maude's comments as "extraordinary".
She told the Today programme: "These allegations should be examined by the proper channels that exist to examine them. "Mr Maude wants to be the Foreign Secretary on Friday, yet he went straight from allegation to penalty without touching ground in between." She added: "There are people whose job it is to look at these things and I have no doubt at all that they will be looked at if Keith Vaz is returned as an MP."
Mr Vaz was told by doctors to take an eight-week break from his ministerial duties after collapsing during a television interview in March.
He is still facing a separate investigation into alleged links between the wealthy Hinduja Brothers and a company run by his wife.
In recent weeks he has been campaigning in his Leicester constituency.