Gordon Brown will tell MPs today that he wants legislation to clean up their expenses system to be rushed through Parliament before the end of the autumn parliamentary session.

He will try to regain the political initiative after surviving an attempt to remove him by setting a tight timetable for a Bill setting up an independent regulator for the behaviour of MPs and peers and a statutory code of conduct for MPs. He will promise that the legislation will be introduced and debated before the summer recess next month and complete its passage when MPs return in October.

Mr Brown intends to open up a debate on electoral reform by making plain for the first time that he is open-minded to change. Ministers say that his actions mark the beginning of the remaking of new Labour.

Rumours circulating at Westminster that he would announce a referendum on proportional representation were denied categorically, but he will declare that a referendum would be needed to scrap the first-past-the-post system. Mr Brown will say that cleansing politics, democratic change and public service reform are his priorities. He was swiftly reminded of the fragility of his position, however, when David Miliband openly named Alan Johnson as “the leading contender” to replace him.

As the new Cabinet met for the first time the power shift away from Mr Brown was underlined when ministers said that next week’s policy announcement, which is being likened to a draft manifesto, would be a reforming event. Several ministers publicly said yesterday that they would hold Mr Brown to his promise to make government more open and consultative.

As well as announcing legislation to introduce an independent regulator of the behaviour of MPs and peers, Mr Brown will also sketch out longer-term constitutional reforms including consideration of fixed-term parliaments and giving local parties the power to “recall” MPs. He will also suggest that he is open-minded about changing the voting system.

Friends say that he is attracted by the alternative vote (AV) system which, while more proportional, retains the links of MPs with their constituencies. This asks voters to list candidates in order of preference, with second or third choices counted until one has 50 per cent support. Mr Miliband said yesterday that the Labour leadership question was “settled”. Ministers and MPs who moved last week to unseat Mr Brown were disappointed that Mr Johnson gave them no encouragement and believe that MPs might have moved towards him had he been less outspoken in his support for Mr Brown.

Mr Miliband, speaking on the Today programme on Radio 4, said: “The Parliamentary Labour Party has reached a settled view about the leadership. The Labour Party does not want a new leader, there is no vacancy, there is no challenger.” He then added: “The leading contender, Alan Johnson, is backing the Prime Minister to the hilt. So that is that.”

Mr Miliband said he always believed that it was right that he should remain in the Cabinet. “I was clear that the right thing to do was to make sure that all of my energies were dedicated to making sure there was a progressive, clear, strong Labour project at the next election,” he said.

He said that, when news came through of James Purnell’s resignation on Thursday night, he had immediately assured Lord Mandelson that he would not follow his exit.

Mr Miliband emphasised that the party’s modernisation project was unfinished. “It’s half-complete in respect of political reform, it’s half-complete in respect of economic reform, it’s half-complete in respect of social reform and, I believe, on the international agenda, it is half-complete too. What I want to work for, what the Prime Minister wants to work for, what the whole Cabinet will work for, is the completion of that project.”

Ben Bradshaw, the new Culture Secretary, said: “I think [Mr Brown] has acknowledged that the style of leadership needs to change. I think he has acknowledged that the way that Number 10 has been operating has not been in the interests either of him or of the Labour Government, that he needs to behave in a more collegiate way.”

Ministers who have long advocated electoral reform have lobbied the Prime Minister with an “intellectual and political case” for the AV system. One said: “We have a huge legitimacy problem and, under AV, we would know that every MP is backed by at least half of the people who voted in their constituency. I have to spoken to Gordon and I think he will do it even if he is not quite ready to push the button that makes it happen.”

A Downing Street source said that Mr Brown was “genuine in saying that he wants a debate about this and [is] not prejudging the outcome — which is itself a change”.

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