The prime minister is expected to renew his appeal for Sir Fred Goodwin to hand back part of his £16m pension at a meeting of Labour activists.
Gordon Brown has reiterated his call for a clean-up of the financial system to ensure what he called "banking responsibility" in the UK and abroad.
Gordon Brown has threatened legal action against the ex-Royal Bank of Scotland (RBS) chief over his pay-out.
He also repeated his promise of legal action to recover pension pay-outs negotiated by bosses of failed banks.
He will also tell Labour's national policy forum in Bristol that more global banking regulation is necessary.
In a speech to Labour activists in Bristol, the prime minister said banks had lost sight of basic moral values.
But he will face a protest by the Communication Workers Union (CWU) at plans to partly privatise Royal Mail.
He outlined his vision for a reformed banking system, and promised banks would help families and small firms.
Sir Fred's pension pot doubled to £16m last October, guaranteeing the 50-year-old £693,000 a year for life, when he agreed to take early retirement.
Mr Brown told members of Labour's National Policy Forum that there had been "the biggest collapse in the banking system that the world had ever seen".
On Friday, the prime minister said he shared public anger at the "unacceptable" pension and was "considering every legal means at our disposal" to get some of it back.
He said: "Our task must be nothing less than to rebuild a financial system where it has failed, and then to create an economy in which banks are no longer serving themselves but are serving the public of this country."
Sir Fred, who stepped down after RBS had to be bailed out by the government, has so far rejected pleas to return it.
Divisions of Labour
The BBC's political correspondent Iain Watson said the prime minister will give a "wide-ranging" speech to Labour activists and trade unionists in Bristol, setting out what he regards as the main dividing lines between Labour and the opposition.
But there are also divisions within Mr Brown's own party, our correspondent said, particularly over the proposed partial sell-off of Royal Mail.
The controversial proposal to sell off 30% of Royal Mail is opposed by more than 120 Labour MPs and led to a protest in Westminster by postal workers on Tuesday.
The government says the Royal Mail needs new investment in technology to survive, but critics fear the scheme will lead to full privatisation and job cuts.
The CWU has threatened to disaffiliate from Labour if the plans, due to be debated in the Commons in June, are enacted. The union donated £53,000 to the party in the last quarter of last year.
Mr Brown is expected to reiterate the message that the majority of the postal business will remain in public hands.
