LONDON (Reuters) — An expenses scandal that has discredited the British political system and fuelled calls for radical reform of the "Mother of Parliaments" looks set to prompt a voter backlash against Prime Minister Gordon Brown. Disclosures that MPs have claimed everything from an adult movie to a chandelier on expenses have infuriated voters, eroding faith in the country's ancient democratic institutions and causing Britain's worst political crisis for years.

The scandal has led one junior minister from Brown's Labour party to step down pending an inquiry while two Labour lawmakers have been suspended and a senior adviser to opposition Conservative leader David Cameron has quit. Other politicians have repaid thousands of pounds claimed on expenses and paid for from the public purse to try to save their reputations and dampen outrage and indignation gripping Britain.

Police are considering whether to launch a criminal investigation in the most serious of the cases, which were published over the last 10 days by the Daily Telegraph newspaper which obtained records of lawmakers' expense claims. Britain's financial markets have yet to show any impact from the scandal. The FTSE-100 share index slipped last week but that was after a near 20 percent rally since mid-March.

The Speaker of the lower House of Commons, Michael Martin, is under pressure to quit over his handling of the expenses crisis and a no-confidence motion against him could be introduced in parliament on Monday, political sources say. "I've arrived at the conclusion that the speaker must go," said Nick Clegg, leader of Britain's third main party, the Liberal Democrats.

"Parliament has been brought into complete disrepute. There is a danger (to) the democratic process itself and the legitimacy of parliament," Alan Rusbridger, editor of the Guardian newspaper, said. "It is quite a dangerous moment."

Britain has one of the oldest parliamentary democracies and the Westminster assembly on London's River Thames is a model for parliaments around the world and traces its origins back to the 12th century when barons and archbishops advised the king.

Voters enduring Britain's worst recession since the Second World War have been incensed to find out that members of parliament have claimed public funds to clean swimming pools and a moat and buy manure for gardens. One even claimed for a bath plug.

Legislators from all the major parties have been involved and polls suggest voters could turn their backs on them at June 4 local and European elections, instead supporting fringe parties such as the far-right British National Party (BNP) or the anti-European Union UK Independence Party (UKIP). Voters are likely to inflict the stiffest punishment for the expenses scandal on Brown's Labour party, in power for 12 years, political analysts say.

Mike Gapes, Labour chairman of parliament's foreign affairs committee, said all parties would be damaged by the affair, but the government the most. "There will be a very low turnout (on June 4) and people will vote for extremist parties. That's my fear," he told Reuters.

A BPIX poll for the Mail on Sunday newspaper showed Labour's expected vote in the European elections falling by six points in a week to just 17 percent. That puts them level with UKIP and 13 points behind the main opposition Conservatives.

That would be a disastrous result for Labour and could lead Labour legislators, fearing a crushing defeat at a general election that Brown must call within the next year, to back a challenge to his leadership of the party. European and local government elections rarely cause market moves regardless of results. Investors are worried about Britain's ballooning debt but, given opinion polls, will not be surprised if Labour loses next year's election.

Influential columnist Polly Toynbee, writing in the left-leaning Guardian, said installing a new leader could be Labour's last chance to avoid a heavy election defeat next year.

Warwick University politics professor Wyn Grant said Brown would probably reshuffle his cabinet after the June poll but believed he was unlikely to face a leadership challenge. Brown's opponents have been unable to gain momentum in the past and potential leadership contenders might prefer to wait rather than lead the party to a likely defeat next year. Britain's 646 legislators receive an annual salary of almost £ 65,000 ($98,830), but also claimed £93 million in allowances last year, an average of £144,000 each.

With big pay rises deemed politically unpalatable, many members of parliament have used expense allowances to supplement their salary and some politicians appear to have been reluctant to disturb the status quo of this anachronistic system. Second home allowances for MPs, working in Westminster and their constituencies, have been particularly controversial.