LONDON - Plans to let police detain terrorism suspects for up to 42 days without charge were dealt a blow on Thursday after an influential parliamentary committee said no case to change the law had been made.

Prime Minister Gordon Brown and Home Secretary Jacqui Smith now face an uphill battle to get the proposal through parliament after the powerful cross-party Home Affairs Select Committee rejected it, saying it could further erode civil liberties.

Brown could now face the same the problems that plagued his predecessor Tony Blair, who suffered his first parliamentary defeat in 2005 when he tried to increase the detention time to 90 days from 28 days now.

Both the Conservative and Liberal Democrat parties, and some members of the Labour Party, have said they would not support the proposals.

"We saw no evidence that there was a case for extending the pre-charge detention beyond 28 days," said the committee's chairman, Labour MP Keith Vaz.

In a report the committee concluded: "We consider that there should be clearer evidence of need before civil liberties are further eroded, not least because without such evidence it would be difficult to persuade the communities principally affected that the new powers would be used only to facilitate evidence gathering and not as a form of internment."

The government says the extension of the period to 42 days would give authorities more time to question suspects in highly-complex terrorism cases.

Senior police officers, including London Commissioner Ian Blair, have backed the proposal.

But both the Director of Public Prosecutions, Ken Macdonald, and the former Attorney General, Lord Goldsmith, gave evidence to the committee saying no change was necessary.

While saying they recognised the "real and acute" terrorist threat, Vaz said the proposals could prove counter-productive for authorities.

He said the government had to consult better to get the laws approved.

The committee concluded the Muslim community might start believing the proposals were a form of internment, unless adequate explanation was given, which had yet to be done.

It said post-charge questioning and the use of evidence from covert phone tapping in court -- which is banned in Britain -- could prove to be better options for police.

The cross-party committee report comes days after Smith gave evidence, where she repeatedly defended the proposals.

The report's authors said they were surprised by Smith's admission that only six out of 71 unnamed organisations which had given their opinion had voiced unequivocal support.

One government MP, David Winnick, voted against the report.

Smith said she welcomed the committee's report despite their negative comments.

"I welcome the committee's view that the current pre-charge detention limit may prove inadequate in future and its recognition of the need to develop proposals to extend it beyond 28 days," she said.

She again defended the proposals, saying that the 28-day limit would only be extended where there was an "exceptional operational need for a temporary higher limit".