Conservative frontbenchers and all Labour MPs are to be asked to register any family members they employ.
Prime minister Gordon Brown said he would make the move applicable to all Labour MPs after Tory leader David Cameron said his move would be a "good first step" on the way to restoring public trust on the issue.
The moves come one day after Conservative backbencher Derek Conway was suspended from the Commons for ten sitting days over overpayments made to his son Freddie. He was also ordered to return £13,161.
After the case attracted significant media attention earlier this week Mr Cameron withdrew the whip from Mr Conway, effectively expelling him from the Tory parliamentary party.
This morning the Tory leader called for "greater transparency and openness" from MPs over their employees, announcing he would begin by asking "my front-bench colleagues" to declare if they employ a member of their family.
"I think it's very important that we demonstrate that MPs do work hard for their constituents," he said in a statement, expressing enthusiasm for spotchecks to ensure family members are doing the work for which they are employed.
Mr Cameron revealed "just over 70" Conservative MPs employ either their husbands or wives in a secretarial role and called for "a change of culture at Westminster".
"For a long time, allowances were seen as a top-up to pay that wasn't increasing. We live now in a different age," Mr Cameron explained.
He defended the right of MPs to employ family members, saying many husbands or wives of MPs "work for them extremely hard".
Mr Brown made the wider-reaching announcement later this morning, but insisted he had discussed the move with Labour whips yesterday.
Nick Clegg told BBC News 24 he was "urging" all Liberal Democrat MPs to follow suit.