KEEPING foreign nationals in overcrowded British jails is costing the taxpayer more than £348 million a year, it was claimed today.

Figures obtained by the Tories show that 15 per cent of the nearly 80,000-strong prison population are from outside the UK.

The largest contingents among the 12,122 come from Jamaica and Nigeria, with 1,490 and 1,070 respectively.

Another 879 inmates are classified as having "unrecorded" nationality - raising questions over why officials have been unable to establish their origin, and what will happen to them when released.

Shadow immigration minister Damian Green, who brought the details to light through Parliamentary questions, said the situation was "truly shocking".

"We seem to attract criminals from all over the world, and the British taxpayer ends up paying for them," he said.

"Many of these criminals come from friendly democratic countries where deportation could be arranged.

"If we could remove the Jamaican prisoners alone we would save £49m a year.

"Why are there nearly 1,000 people who have gone through the criminal justice system and been jailed without finding out where they come from?"

Mr Green used the "snapshot" figures from the end of February to calculate costs based on government estimates of £33,000 annual expenditure for each prison place.

Some 164 nationalities are represented in British jails, according to the data.