MPs have sent the Identity Cards Bill back to the House of Lords with a warning from Charles Clarke that peers should not continue to reject a key plank of the government's plans.

The home secretary rejected opposition suggestions that linking ID cards to passport applications from 2008 would mean they become compulsory in all but name.

MPs had already twice voted in favour of the proposal, but the House of Lords has repeatedly rewritten the Bill to drop the link to passports.

In a vote on Monday night the Commons decided by 310 to 277 to again back the government.

However the majority of 33 was less than half the government's working majority.

The Conservatives and Liberal Democrats argue that the link between ID cards and passports would mean 'compulsion by the back door', in breach of Labour's manifesto pledge to begin with a "voluntary" scheme.

But Clarke told MPs on Monday night he was sticking to his guns.

And in a sign of frustration with peers, he said he was making the case to reject the Lords amendments "yet again".

He warned the upper house it was "now time for their lordships to accept that the Identity Cards Bill should pass without further amendment".

And he insisted: "Passports are voluntary documents, of course they are.

"No one is forced to renew a passport if they chose not to do so.

"That will remain the case once we begin issuing identity cards alongside passports."

And the home secretary argued that linking cards to passports was "a central part" of the ID scheme.

The data "is being collected in any case when people get their passport renewed", he added.

Clarke also told MPs that the Lords amendments to make ID cards optional for anyone renewing or applying for a passport would increase costs, reduce benefits and inconvenience the public.

It would also offer an "open goal" to fraudsters, criminals and immigration offenders by allowing them to avoid the need to join the national identity register.

In a similar vote last month, 20 Labour MPs rebelled against the government, which won with a majority of 31.

The legislation now returns to the Lords later this week.

With Conservatives and Liberal Democrats insisting on their position, a showdown between the two houses of parliament is looming.