The move follows random tests in April of members of the 1st Battalion Royal Scots, currently based in Colchester, Essex, and the Queen's Dragoon Guards who are at Catterick, Yorkshire.

There is not another organisation we believe that has as good a record on drugs on us

MoD spokesman

Seven members of the Queen's Dragoon Guards and eight members of the Royal Scots failed the tests. None were officers.

The final decision on the future of the soldiers now rests with their commanding officers although it is "highly likely" the men will be dismissed from the Army, said the MoD.

The army has a zero-tolerance policy on drugs as it cannot not afford to have men and women operating multi-million pound equipment under the influence of illegal substances, an MoD spokesman said.

Drug testing in the Army was introduced in 1995, since when 323,000 male and female soldiers have been tested.

Zero tolerance

The drugs tests, which are carried out with less than 24 hours notice, are for any illegal substance, including cannabis, heroin and cocaine.

"There is not another organisation we believe that has as good a record on drugs on us," said the spokesman.

"We put this down to our drugs education programme and our strict policy of zero tolerance."

About 1,600 soldiers have tested positive since the start of testing.

The MoD said 70 more had refused to take the tests and 330 had traces of drugs in their system.