The UK has warned America that it will cancel its £12bn order for the Joint Strike Fighter if the US does not hand over full access to the computer software code that controls the jets.

Lord Drayson, minister for defence procurement, told the The Daily Telegraph that the planes were useless without control of the software as they could effectively be "switched off" by the Americans without warning.

"We do expect this technology transfer to take place. But if it does not take place we will not be able to purchase these aircraft," said Lord Drayson.

The problem stems from strict US guidelines on the transfer of technology to other countries. Under current rules any British requests for the use of US technology can take 20 days to go through, obviously limiting the usefulness of a jet strike force.

Lord Drayson is currently in Washington to speak to members of Congress. His tough talking on the project includes the fact that Britain has a 'Plan B' if the Joint Strike Fighter deal falls through.