The spotlight turned on opposition Conservatives on day four of newspaper revelations detailing how MPs dipped into the public purse for cottage decorations and repairs to a water pipe under a tennis court.

Parliamentarians 'have a responsibility to show that people who enter our profession are there to serve the public interest, and not to serve themselves,' Mr Brown said.

A survey on Sunday showed that 89 percent of respondents said the reputation of MPs had been damaged by the nature of the previously secret claims.

A new poll published late Monday, carried out since the revelations began on Friday, suggested the two main parties were taking the biggest hit in support.

The Populus poll for the Times showed Brown's Labour party on 26 percent and the main opposition Conservatives on 39 percent, both down four points on last month. Support for the smaller Liberal Democrats is up four to 22 per cent.

Brown's apology came after Conservative leader David Cameron also urged lawmakers from all parties to say sorry. Mr Cameron said it was 'not good enough' for parliamentarians to claim they were simply following the rules allowing them to claim expenses.

The Daily Telegraph newspaper, which reportedly paid a six-figure sum to buy the CD containing details of the claims, turned its attention to the Conservatives on Monday after three days of detailed revelations about Labour.

Mr Cameron himself emerged unscathed by the revelations, while Brown is still fighting off accusations that he abused the system by paying his brother 6,000 pounds for arranging cleaning services for his private home.

The drip-drip of revelations has led to calls from Mr Brown and Mr Cameron for the expenses system to be overhauled - and House of Commons speaker Michael Martin confirmed proposals for a 'serious change' to the system of MPs' allowances. -- AFP