Tony Blair's government has become arrogant and does not take fighting sleaze seriously enough, former Commons Speaker Betty Boothroyd has said.
Betty Boothroyd is worried about the size of Blair's majority
Baroness Boothroyd, a former Labour MP, said the government had enjoyed "far too large a majority".
This meant it was "steam rolling over everything", she said, adding that Mr Blair was too presidential.
She backed standards watchdog Sir Alistair Graham for saying Mr Blair saw standards as a "minor issue".
She told BBC News 24's Straight Talk programme: "It was absolutely right for a man in that position to speak out as he has done and I hope that 10 Downing Street have taken note of that."
The prime minister came to power promising to be "whiter than white".
But Lady Boothroyd, who stepped down as Commons speaker in 2001 and sits as a crossbench peer, spelt out what could go wrong in power.
"It came in with very good intentions, making all those statements, setting up all these conventions, these institutions - quite right," she said.
"But somehow there is an arrogance that has been built in there because they feel that it doesn't quite affect them."
Downing Street insists it does take standards issues seriously.
Sir John Bourn was appointed in March to advise ministers on potential clashes between their public duties and private affairs - and to investigate any claims that the rules have been broken.
But Sir Alistair has said he has little discretion to act on his own initiative and there is no guarantee his findings will be published.
Lady Boothroyd said she had prayed at the last election for whatever government was elected to have a "nice majority" of 30 or 40 (Labour's majority is 66).
"Otherwise there is arrogance, there is steam rolling over everything," she said.
The British prime minister now goes all over the world and is a world statesman, she said.
"So it is a bit presidential with a small 'p' in that respect, but for goodness sake let us not move into presidential style," she argued.
Lady Boothroyd also attacked the idea of having a partly-elected House of Lords, a proposal which reportedly now has Cabinet backing.
"I've never heard how that's going to work," she said. "Are my votes less important than somebody who's been elected?"
She argued that a fully elected Lords would be a "huge challenge to the primacy of the Commons".
She asked who would "reign supreme" if the two houses disagreed.
Meanwhile, Mr Blair's former policy adviser is warning that Labour has lost public trust by relying too heavily on rich backers.
Geoff Mulgan, ex-No 10 policy chief, said the increase in spending by political parties on elections in the 1980s and 1990s had created pressures.
"I think many of them paid much to high a price in terms of giving too much power and sway to rich individuals and big companies," Mr Mulgan tells GMTV in an interview to be broadcast on Sunday.
"Then, not surprising, the public lost trust in them because they saw that happening, and I fear that that has happened to some extent to New Labour."
But he said the UK had been blessed "with pretty impressive leaders and highly moral leaders by the standards of recent history, or indeed by international standards".
Mr Blair ordered a review of the way parties under funded after recent claims of "cash for peerages".
New limits on election spending and on the size of individual donations are among the options being considered by former civil servant Sir Hayden Phillips.
Lady Boothroyd's Straight Talk interview is being screened on BBC News 24 on Saturday at 0430 BST, 1030 and 2230, and on Sunday at 0130, 1530 and 2230.