Lord Falconer has defended the government's latest anti-terror plans despite reports that they could be ruled illegal by senior judges.

The constitutional affairs secretary said the plans to introduce house arrest without trial for foreign nationals and British citizens would not lead to a "police state".

But his comments followed reports that attorney general Lord Goldsmith had advised fellow ministers that the proposals could be challenged in the courts.

The Sunday Times quoted one unnamed minister as saying that the attorney general "said that the plans for home detention run the risk of being overturned".

Lord Falconer, however, insisted that the proposals would be approved by parliament and make it on to the statute book.

"We as a nation do face, I believe, a very severe terrorist threat, which since 9/11 has been different and much stronger than other terrorist threats," he told the BBC.

"We as a government, as one of our main obligations, have to protect the public from that threat, but we have got to do it within the law."

He said that having the current detention policy ruled illegal "doesn't absolve us as a government from seeking to strike that balance".

"What do you do when you have got intelligence, say, from another country, which suggests there will be a brutal attack on some public place?

"If the way you foil that is to make sure that there's some restrictions on what an individual can do, subject to the approval of the courts, that doesn't seem an over-reaction.

"We have got to strike a balance. We can't walk away from the obligation to protect the public."

He also insisted that the proposals would not amount to internment, as the home secretary would have to present the evidence against a suspect to a senior judge.

"That is not internment. That is not a police state. That is a sensible measure," Lord Falconer said.