The Tories believe the problem is worse than the figures show

Scottish Executive figures have shown that the biggest increase was in Fife where the number rose from seven to 88.

There were also large increases in the Highlands and Dumfries and Galloway.

The Conservatives said the figures showed a serious problem but ministers said some of the increase could be due to better data collection.

The figures were released in response to a parliamentary question from Margaret Mitchell, justice spokeswoman for the Scottish Conservatives.

This makes a mockery of the executive's much-trumpeted commitment to early intervention Margaret Mitchell Scottish Conservatives

In 1995-96 there were 124 under 16s in rehabilitation because of addiction. The figure had risen to 418 by 2004-05.

In the Highlands there were 36 cases of under 16's receiving treatment last year and in Dumfries and Galloway there were 20. Neither area had any recorded cases 10 years ago.

The Conservatives warned that the figures were unlikely to reveal the true extent of the problem.

Ms Mitchell said: "With recent cases such as the 11-year-old girl from Glasgow collapsing after smoking heroin, it is evident that the executive's strategy for dealing with drug abuse in Scotland is in tatters."

"This makes a mockery of the executive's much-trumpeted commitment to early intervention.

"Quite simply, it doesn't have to be like this."

'Strong programme'

Deputy Justice Minister Hugh Henry said the increased numbers were likely to be down to an increased focus on the importance of record keeping and more young people taking up treatment.

An executive spokesman said: "We've got a very strong programme in terms of education.

"We've got drugs education in every school and we've also got the very successful Know the Score awareness-raising campaign, which will give young people the information they need.