Britain's politicians should be barred from taking their summer holidays until the constitutional crisis sparked by the expenses row is resolved and "every nook and cranny" of the political system is reformed, Nick Clegg declares today.

In a provocative Guardian article, the Liberal Democrat leader outlines a 100-day action plan to transform MPs' expenses and accelerate the constitutional reforms started in 1997 by Tony Blair.

"Let us bar the gates of Westminster and stop MPs leaving for their summer holidays until this crisis has been sorted out," Clegg writes in the latest high-profile contribution to the Guardian's New Politics series.

"I'm setting out a plan of action to get all the changes we need delivered in just 100 days – making it possible for MPs to be sacked by their constituents, abolishing the House of Lords, getting corrupt money out of politics and changing the electoral system to give a voice to everyone."

Clegg's intervention came as two senior ministers joined the calls for change. David Miliband, the foreign secretary, tells the Guardian that British politics is facing a "dangerous time", as he voices support for electoral reform. Tessa Jowell, the Olympics minister, will say in a speech next week that Labour should select its parliamentary candidates in open primaries.

Clegg, who regards the proposals floated by the two main parties as too timid, attempts to assume the mantle of Britain's boldest reformer when he sets out a week-by-week plan to achieve the "total reinvention of British politics".

In the first two weeks parliament would agree to accept the recommendations of the review into MPs' expenses and allowances by the standards watchdog, draw up a bill to allow for the recall of errant MPs, and impose a £50,000 cap on individual donations to political parties in any year.

Constitutional reforms would then be introduced:

• By week three legislation would be passed to introduce fixed parliamentary terms of four years from 2010, denying the prime minister the right to name the date of general elections.

• By week four the new Commons Speaker would convene all-party talks to introduce a series of changes to parliamentary procedure that would be agreed by day 100. These include handing MPs the right to decide the parliamentary timetable ­and giving MPs a greater chance to scrutinise government spending and subject ministers to confirmation hearings.

• By weeks four to five parliament would pass legislation to allow a referendum to be held on electoral reform – the alternative vote-plus system proposed by the late Lord Jenkins – that would be held on day 100.

• By weeks six to seven parliament would pass legislation to replace the House of Lords with a wholly elected senate.

Clegg said the crisis over expenses provided a historic opportunity to act. "Finally the dam has broken and every­one is talking about changing Britain's political system. For decades, political reformers have been thwarted by the inertia of Westminster. But the expenses scandal has overturned old certainties and made change possible. This moment must be seized by all those who want a different kind of politics in Britain. Warm words, rhetoric and consideration are not enough; indeed they are a guarantee that little will happen."

Clegg believes the expenses crisis marks a significant moment for him – he has railed against the "gentlemen's club" of Westminster since his election as an MP in 2005 – and for the Liberal Democrats, who have campaigned for major constitutional reform for more than a century. He believes his proposals are more radical than David Cameron's.

"David Cameron's proposals set out in the Guardian on Tuesday were a masterful example of well-judged rhetoric free of substance and conviction," Clegg says of the Conservative leader's plans to give "serious consideration" to introducing fixed parliaments. "They are designed, I fear, to provide verbal cover for maintaining the status quo."

Clegg's article comes as the pace of reform picks up. Miliband makes clear he believes in reform when he tells the Guardian today that he supports the alternative vote system.

"If you ask me if this is a good moment for constitutional reform, the answer is yes. It's important that we recognise that this is about the pay and expenses of MPs, but it's about more than that. It's about a political system and political culture that has become too much of a gentlemen's club. This is a dangerous time for British politics and British democracy and the mainstream parties have to show that we get it."

Paul Kenny, general secretary of the GMB union, warned that at least 50 Labour MPs might be forced to stand down for inappropriate expenses claims, with up to 100 MPs leaving Westminster.

His remarks came as Tory MP Julie Kirkbride, a former shadow culture secretary, faced fresh pressure over her expenses. Hours after she had robustly her "complicated" expenses, the Daily Telegraph reported that Kirkbride had used her parliamentary allowance to help fund a £50,000 extension to her constituency flat to accommodate her brother.

Kirkbride said she had done nothing wrong, because her brother looks after her young son, Angus. The extra space was needed as Angus grew up.

Kirkbride is under pressure after her husband, fellow MP Andrew MacKay, announced he would stand down over his housing allowance. MacKay designated Kirkbride's constituency flat as his main home, allowing him to claim allowances on their London home.