A report in Thursday's Daily Express newspaper said worried soldiers were calling the National Gulf War Veterans and Families' Association because of health concerns over the vaccine.

An association spokesman told the paper: "They (the soldiers) are being told there is a risk of being deployed to an area of operations where anthrax may be deployed.

"The vaccine takes 26 weeks to become effective. This is obviously the start of something big."

'No plans'

But Mr Hoon said there was no change to the routine vaccination programme under which troops are regularly protected against a variety of illnesses.

He told the BBC: "There has been a programme of vaccination for some time now."

Mr Hoon said the drive was nothing new and it was up to the troops whether they participated.

He also restated that Britain had no plans for military action "at the present time" in relation to Iraq.

The United States, which fears Iraqi president Saddam Hussein is accumulating weapons of mass destruction, has been hinting that an attack on Iraq might be the next step in its "war on terror".