Former cabinet minister Robin Cook has defended Commons leader Peter Hain for voicing his ideas on changing the tax system.
Cook said Hain was "an immense asset"
Mr Hain had intended to call for top earners to pay more income tax during a speech to a left-wing think-tank, but was forced to drop his suggestion after criticism from the government.
Both Prime Minister Tony Blair and the Treasury made it clear there would be no change in tax policy.
Mr Cook said that while he did not agree with Mr Hain's suggestion, ministers should be encouraged to discuss their ideas in public.
But Foreign Secretary Jack Straw told the BBC the tax issue was too sensitive for ministers to debate in public.
Mr Cook said: "I think Peter Hain is an immense asset to the cabinet precisely because he's thinking for himself and saying things which may be original and difficult.
"I happen not to agree with him on the top rate of income tax, but I actually think people should be allowed to murmur in public when they have got private thoughts about it," he told BBC Radio 4's Any Questions programme.
Robin Cook: "Party discipline too tight"
People were doing "immense damage to politics by insisting on too tight party discipline," added Mr Cook, himself a former leader of the House of Commons and foreign secretary.
He said one of the big reasons people were turning off politics was because they did not see enough politicians "thinking for themselves, saying original things and speaking from the heart and from conviction".
But Mr Straw defended the government's response to Mr Hain's comments and issued a warning against re-opening old wounds over tax.
"Governments have some key debates internally and then we have a policy and that policy is reflected in decisions which are taken," he told BBC Radio 4's Today programme.
"Tax is a sensitive issue, not only for the government. It is a sensitive issue for all governments and all parties.
"Because of its sensitivity it is an issue which has always been handled and initiated by the Chancellor of the Exchequer.
"We have, after what was a very painful period in the 1980s and early 1990s, which I recall all too well, got a good and settled policy in respect of tax."
In his speech, Mr Hain cut his planned comments and instead spoke of the need to consider radical steps to narrow the gap between rich and poor and ensure fairness in the tax system.
BBC political correspondent Carole Walker says his retraction was a climbdown for someone who has enjoyed a reputation as one of the free-thinkers of the Labour government, BBC political correspondent Carole Walker.
'News to me'
Mr Hain told the Cardiff audience: "Let me make clear... we will not raise the top rate of tax and there is no going back to the old days of punitive tax rates to fund reckless spending."
Earlier however, he had spoken of there being "hard choices" on tax ahead and mooted the possibility of high earners may have to pay more.
In an interview on the Today programme on Friday, Mr Hain said too many people on average incomes - including teachers and police officers - now fell into the 40% income tax band.
He said in order to help those on low and middle incomes the top earners could be asked to give more.
Delivering the Aneurin Bevan lecture, he said a lot of what had been reported earlier was "news to me".
He said the government was not planning to go back to "the old days" of high taxes.
Instead, he said, he had simply wanted to ask "hard questions on the issue".
Opposition parties also directed fierce criticism at Mr Hain.
Shadow chancellor Michael Howard said it represented "the slipping of the last of the veils from New Labour".