LONDON- Prime Minister Gordon Brown will unveil proposals on Tuesday to rebuild the image of parliament tarnished by a scandal over lawmakers' expenses, and in so doing seek to restore his ailing popularity.

The reputation of MPs has taken a battering after details of extravagant and often inappropriate claims for public money to pay for things from dog food to cleaning a moat were published by a newspaper.

Public anger and distrust was compounded when officials finally published their allowance claims in a heavily censored format with black marks covering key details.

Although MPs from all major parties have been embroiled in the expenses row, Brown's government has suffered most after failing to reform the system since taking power in 1997.

Brown, battling with the worst recession since the Second World War and trailing the Conservatives by up to 20 percent in polls less than a year before the next parliamentary election, has been striving to regain the initiative.

Writing in the Daily Mail paper, he said he would propose legislation on Tuesday to create an independent regulator to oversee MPs and to ensure they abided by a new code of conduct.

Parliament badly let people down and they are rightly angry, he wrote.

The strength of their revulsion was clearly expressed in the local and European elections earlier this month, he said, referring to polls which saw his Labour Party slump to its worst performance in a nationwide vote since 1990.

After the results, Brown survived calls from senior colleagues to resign to give Labour a fighting chance of winning an unprecedented fourth straight election win.

Brown, who has expressed his determination to stay on and clean up politics, said under his proposals those MPs who failed to abide by new rules would face sanctions.

We have learned our lesson -- that without proper accountability, political institutions become vested interests, existing in a moral vacuum, he wrote.

On Monday, MPs elected John Bercow, a moderate Conservative, as Speaker of the House of Commons, replacing the previous incumbent who was forced to step down over criticism of his handling of the expenses affair.

Bercow has promised reform after the scandal, which has ended the careers of more than a dozen MPs who have said they will not stand at the next election.

Last week, police said they would investigate the expense claims of some MPs.

A number have paid back thousands of pounds after they were found to have abused the system in a variety of ways.

They include Conservative leader David Cameron, tipped to be the next Prime Minister, who said he would repay almost 1,000 pounds he had mistakenly claimed.

(Reporting by Michael Holden)