Downing Street has refused to comment on the attorney general's scepticism about the government's anti-terror plans.

Lord Goldsmith has indicated publicly he is not convinced by Charles Clarke's plans for terror suspects to be detained for up to 90 days.

But Number 10 said on Monday that it would not comment on "internal government discussions".

"What we are determined to do is consider very, very seriously the requests of the police in this matter," the prime minister's official spokesman said.

Both the home secretary and prime minister have given their backing to the proposals, which are being sought by the Association of Chief Police Officers.

Under current rules, suspects can only be held for up to 14 days without charge, but the government says this can provide insufficient time to gather crucial evidence.

And in an unusual sign of dissent, Lord Goldsmith has indicated he is not prepared to back an extension to 90 days.

The law chief's spokesman told the Times: "He believes the case is there for longer than 14 days but is not convinced he has seen a case for 90 days."

While this did not mean he would not support the longer extension in future he had yet to see evidence to support such a move.

In a letter to the Home Office, written in his capacity as a Cabinet minister rather than as a legal opinion, Lord Goldsmith also called for any extension to be subject to "rigorous judicial scrutiny".

In a sign of wider legal opposition to the plans, former law lord Lord Steyn also said the planned extension was an "exorbitant and unnecessary power".

"If you ask me why the government seeks this power, I can only say that governments always seek more and more powers. They are not always right," he told the Telegraph.

Speaking on Sunday, Commons leader Geoff Hoon had indicated the government could be prepare to compromise on the proposals, which are being opposed by both the Conservatives and Liberal Democrats.

"We have made clear all along that this bill is for discussion and debate," Hoon told BBC Radio 4's The World this Weekend programme.

"We have recognised it does contain a number of measures which will excite interest. We will listen to the opinions set out in parliament and act accordingly."