The home secretary has been urged to drop plans to close an immigration checkpoint at London's Waterloo station.

Immigration officers launched a legal bid on Thursday to halt the Home Office proposal, claiming that up to 200,000 Eurostar rail passengers have been allowed into Britain without passport checks.

David Blunkett wants checks to take place at the start of journeys in Brussels and Paris in order to prevent passengers claiming asylum in the UK when they could do so in other parts of the EU.

But 80 Immigration Service officials have tried to stop the move, claiming the checks in Belgium and France are not rigorous enough.

Through law firm Wedlake Bell they sent a letter to Blunkett asking that the plan subjected to judicial review.

"The records show that approximately 200,000 passengers have entered Waterloo International Terminal in the last 18 months without being subjected to any form of immigration control," the letter said.

"Around 160 trains have entered the UK without any checks at all."

While travellers could make asylum claims in Britain as soon as they are through the Brussels or Paris checkpoints, the staff argue that the Waterloo office should remain open as a last line of defence against security risks such as terrorism.

And the Belgian government has not yet given Britain full rights to perform immigration checks on its soil.

The letter said closing the London checks before the new system is in place would be "an obvious risk in relation to security concerns and illegal immigration".

Shadow home secretary David Davis said Blunkett was repeating previous mistakes.

"This is another Home Office shambles. They have started down this road before offshore controls appear to be working properly," the Conservative said.