MPs have criticised government plans to hold terror suspects beyond 28 days.

The home secretary announced last week that the government wanted to increase the limit of pre-charge detention to 42 days in "exceptional" circumstances.

And appearing before the Commons home affairs committee on Tuesday, Jacqui Smith said that there was a "potential future requirement" for the move.

She told MPs she was "trying to garner support" on the issue, but acknowledged that "there doesn't appear to be a consensus".

Smith pointed to plans to give Parliament the final say on whether a suspect should be detained, something Labour backbencher David Winnick described as a "cosmetic exercise".

Winnick said it was "misleading" to describe the measure as a safeguard, because a suspect could already have been held for 42 days before Parliament was given a vote.

And Conservative James Clappison said the parliamentary vote would be "meaningless".

But the home secretary argued that the "spectre of Parliament" would preside over the decision.

Smith admitted that just six out of the 71 respondents to a consultation "unequivocally" supported moves to increase the current limit.

But accepting that there had not been a case to date when more than 28 days had been needed, she said there is "at least a possibility" where it might be in the future.

Tony Blair was voted down in the Commons in 2005 when he attempted to push through legislation to increase the period of pre-charge detention to 90 days.

And the current proposals have been criticised by the Conservatives and Liberal Democrats, as well as Labour MPs and human rights groups.

The director of public prosecutions also said more than 28 days had not been needed so far, and former attorney general Lord Goldsmith said he would have resigned from Blair's government had it succeeded in its attempts.

Winnick suggested that the government had proposed 42 days in an attempt to gather backbench support for an extension, but Smith said she "fundamentally disagreed" with this.

"It's being done, not to buy political support but to provide the police and those that we task with protecting us from terrorism with the tools that they need to do the job," she argued.