Oliver Letwin has warned that the European arrest warrant is a threat to British civil liberties.

Joining campaigners to hand in a petition to Downing Street, the shadow home secretary said euro-arrest powers represent "a serious and unwarranted attack on the civil liberties of all those resident in the United Kingdom".

Opposition to the European arrest warrant is being backed by human rights campaigners Liberty.

Queen's Speech moves to modernise extradition legislation will enact the EAW and could see UK citizens extradited for offences that are not crimes in Britain.

"We believe that extradition should only apply to serious offences to guard against thousands of individuals being sent abroad for very minor or trivial offences," says the petition.

"We also believe that the list of offences in the bill that can give rise to extradition is too vague and too wide and includes unacceptably ambiguous offences such as 'computer related crime'."

Letwin spoke at a Commons "freedom rally" to highlight concerns about the EAW, which is expected to face a tough passage through the House of Lords.

The shadow home secretary said that too many of the crimes covered by the warrant were "vague and undefined".

"This is a gross infringement of our civil liberties and would lead to our citizens facing trial in other countries, some of whose legal systems operate on the presumption of guilt," he said..

"We will be opposing the enforcement of the European arrest warrant in the forthcoming Extradition Bill."