Mr Brown will update the House of Commons on progress towards the introduction of an independent regulator for Parliament in the wake of the scandal over MPs' expenses, his spokesman said today.
The move - designed to show Mr Brown has a forward-looking agenda on one of the key causes for voter disillusionment with politics - came as Foreign Secretary David Miliband declared that Labour had "settled" its leadership question.
In an attempt to draw a line under the failed efforts to oust Mr Brown, Mr Miliband said that even the "leading contender" to replace the PM, Home Secretary Alan Johnson, was backing him "to the hilt".
Mr Miliband said that when news came through of James Purnell's resignation from the Cabinet on Thursday night, he immediately assured Business Secretary Lord Mandelson that he would not follow his exit.
However, he dodged the question of whether he "flirted" with the idea of resignation, saying only: "Flirtation is dangerous for married men, I'm not going to get into that."
Mr Purnell today insisted he stood by his call for Mr Brown to stand down to give Labour "a fighting chance" in the general election expected next year.
Despite failing to trigger a walk-out of senior Cabinet ministers, he said he did not regret quitting as Work and Pensions Secretary, adding: "I said what I said, I stand by it."
Mr Miliband told BBC Radio 4's Today programme: "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.
"The leading contender, Alan Johnson, is backing the Prime Minister to the hilt. So that is that."
He added: "I always believed that the right thing to do was to 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."
Mr Miliband admitted the odds were "stacked against" Labour winning a fourth term in office.
His comment about Mr Johnson will raise questions at Westminster over whether the Foreign Secretary - suspected last year of planning a leadership bid - has given up his own ambitions to succeed Mr Brown.
The immediate threat to Mr Brown's position receded today after he faced down backbench critics at a make-or-break meeting of the PLP last night.
Despite catastrophic results in European and council elections and a string of ministerial resignations, only a handful of MPs called for him to quit, after a speech in which he admitted to "weaknesses" and promised a fresh approach and new policies.
The Prime Minister was today able to complete his ministerial reshuffle without further resignations, and brought Shahid Malik back into his Government as a junior communities minister after the Dewsbury MP was cleared by an inquiry of irregularities relating to his housing arrangements.
Mr Brown today chaired the first meeting of the National Democratic Renewal Council, set up to develop policies for reform of Parliament following the expenses scandal.
Tomorrow's statement will spell out the Government's position on issues ranging from a new code of conduct for MPs to strengthening the role of parliamentary select committees in scrutinising the executive, as well as looking at the wider debates on reform of the House of Lords and the modernisation of voting methods for Westminster elections.
Mr Brown is likely to unveil legislation to end the system of parliamentary self-regulation and create a statutory independent parliamentary standards authority, so that MPs will no longer decide their own pay and expenses.
As well as moves on democratic reform, attention will focus on any signs of a new approach by the Prime Minister following last night's humble address to the PLP.
There are expectations of an inquiry into the Iraq War and a compromise over the part-privatisation of Royal Mail to be announced soon in a bid to win over disgruntled Labour backbenchers.
Labour's annual conference in September could yet become the focus of any further uprising against Mr Brown, should the party's fortunes fail to improve by then.
New Culture Secretary Ben Bradshaw said today that Mr Brown had acknowledged that the style of his 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," said Mr Bradshaw.
And Scottish Secretary Jim Murphy urged the PM's advisers to stop trying to "turn him into something that he's not" with ideas like having him discuss his taste in music in public.
"He should leave the superficial spin and nonsense to David Cameron and concentrate on what he's great at, which is being a man of substance dealing with the enormous challenges our country faces today and in the future," said Mr Murphy.
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