The Conservatives have claimed that the government will announce plans tomorrow to make identity cards compulsory for airport workers.

Shadow home secretary David Davis said he believed Home Secretary Jacqui Smith will make the announcement on Thursday in breach of an undertaking not to introduce compulsion without a prior vote by MPs.

About 100,000 airside staff are expected to be covered in a statement from Smith to MPs, which is thought to be in line with leaks last month indicating a national rollout is being postponed to 2012 but that workers in sensitive locations would be covered sooner.

"It is inconceivable that these workers would not already have full ID verification,” said Davis.

“Therefore the question has to be: Will this add to airport security or is it a way of getting the British public used to an ID card by stealth, despite an explicit promise from a former home secretary that this programme would not be rolled out in a compulsory fashion without a vote in the Commons?."

A home office spokeswoman said the intention is to start with "certain parts of the population" and proceed incrementally, and the first priority would be where it was considered of greatest benefit to the security of the UK.