UK lawmakers voted Thursday in favour of stripping naturalised terror suspects of their British citizenship, a last-minute amendment to an immigration bill facing a bumpy ride through parliament.

Home Secretary Theresa May introduced the amendment which would allow a British passport to be removed from any naturalised person whose conduct is deemed "seriously prejudicial to the vital interests of the UK".

The bill is part of the Conservative-led coalition government's attempts to toughen up the immigration system, with a general election due in 15 months' time and the anti-immigration UKIP party applying pressure.

Rebellious Conservative backbenchers feel it does not go far enough on foreign undesirables and the last-ditch proposal was an apparent effort to appease them.

May already has the power to strip British citizenship from people with dual nationality.

The new proposal would allow the interior minister to strip citizenship from naturalised Britons regardless of whether they possess another passport, and could therefore make them stateless.

The amendment carried by 297 to 34, with the main opposition Labour Party abstaining and a small number of Liberal Democrats -- the junior party in the governing coalition -- voting against it.

"Those who threaten this country's security put us all at risk," said Immigration Minister Mark Harper.

"Citizenship is a privilege, not a right. These proposals will strengthen the home secretary's powers to ensure that very dangerous individuals can be excluded if it is in the public interest to do so."

Deputy Prime Minister Nick Clegg, the Liberal Democrat leader, said May's amendment was "controversial but I think it's justifiable", telling LBC radio it would only be used for a small number of cases of people who pose a "real, real threat" to Britain's security.

The amendment was seen as an attempt to appease Conservative rebels, who proposed their own amendment which would have given ministers rather than judges the final say on whether deportation would breach the rights of foreign criminals.

That was defeated by 241 votes to 97, only failing due to Labour and Lib Dem opposition.

Labour's home affairs spokeswoman Yvette Cooper accused May and Cameron of being "scared of their own backbenchers".

Thursday's debate in the House of Commons completed its passage through the lower chamber of parliament. It will now be sent to the upper house, the House of Lords, for consideration.

The bill would allow the deportation of foreign criminals before the outcome of their appeal, with the number of grounds for appeal slashed from 17 to four.

It would also force landlords to verify whether their tenants were in Britain legally, while banks would have to do likewise before allowing them to open accounts.

Some temporary migrants would pay a £200 ($330, 240-euro) annual levy towards the state-run National Health Service.

Registrars would have to tell the Home Office about planned weddings between British citizens and those from outside the European Union, in a bid to clamp down on sham marriages.