Britain's biggest police force is to forge a unit of foreign officers in a bid to tackle the growing threat from overseas offenders.

The Metropolitan Police said it has requested €2.2 million (£1.9m) of European Union funding to allow officers from other countries to be seconded to the force. Romania and Poland have agreed already to sign up.

The officers would share intelligence and join Met officers on operations, Scotland Yard said, but it is understood they would not have powers of arrest.

The top 10 countries of origin of those arrested are Romania, Nigeria, Somalia, Jamaica, Lithuania, Portugal, Poland, India, Pakistan and Ireland, with 40% of all foreign national offenders from these countries, the Met said.

Some 28% of those arrested for a criminal offence in London are foreign nationals, recent Met intelligence showed.

Up to 30 officers would be deployed initially for three years, according to The Times newspaper, and would operate mostly in plain clothes but be able to wear national uniforms if required.

The Met is reportedly in talks with police in Lithuania and Ireland to join the unit, but if successful it could be widened.

The unit is understood to form part of Operation Nexus, which combines police and immigration intelligence to tackle foreign criminals in London and has led to the removal of some of the capital's highest-harm criminals.

More than 300 foreign criminals have been deported since the joint initiative launched by the UK Border Agency (UKBA) and the Metropolitan Police Service at the start of September.

But the move is likely to add to confusion over UK-European relations as home secretary Theresa May seeks to withdraw from a raft of EU police and justice agreements.

Mrs May last October said the government intends to opt out of 130 measures, including the European Arrest Warrant, but is then likely to apply to opt back into some of the cross-border agreements which it thinks are in the national interest.

A UK Border Agency spokesman said: "Foreign nationals who break our laws should be removed at the earliest opportunity and Operation Nexus is already proving a success, with nearly 300 foreign national offenders, including high-harm gang members, being removed from the UK since September.

"By combining expertise and intelligence with the Met, we are speeding up the removal process and using the full force of immigration powers on those who seek to abuse the system, commit crime and damage our communities."