Head teachers will be given powers to introduce random drug testing in their schools, the prime minister has told a Sunday newspaper.
Parents will be told if drug-testing is being used at their child's school
In an interview with the News of the World, Tony Blair said the guidance will be issued next month.
Heads will have the power to either offer treatment to young users, exclude them or report offenders to police.
But the plans have been condemned by the Liberal Democrats and civil liberty campaigners.
The Department for Education and Skills disclosed earlier this year that it was looking at new guidelines for head teachers in England, which it had planned to publish this month.
But it had not previously been clear whether they would extend to random testing.
"If you have a serious problem in your school there is no point in trying to conceal it," Mr Blair told the paper.
Results from an ICM Research poll which appears in the News of the World on Sunday suggests 82% of parents and 66% of children support drug testing in schools.
Of the 1,000 parents surveyed, 96% said they would want to know if their child was taking drugs.
Mr Blair told the paper head teachers could not be forced to introduce drug testing, but said they should have the option if they believe there is a problem in their school.
"Some head teachers may worry that if they go down this path they are declaring there is a problem with their school," said the prime minister.
"But in my view the local community is probably perfectly well aware that there is a problem."
However, Lib Dem education spokesman Phil Willis told BBC Radio 4 that he strongly objected to the principle of random drug testing.
He said: "Are we going to do the same for smoking for underage children? Are we going to do it in terms of drink? Is that how we are going to create civilised communities in our schools, because I just don't believe that is the way?"
Tory education spokesman Tim Collins welcomed the announcement, but said it also sent out mixed messages given that the government had just eased the laws on cannabis.
Barry Hughill from civil rights group Liberty said he could not understand how the new powers would help.
"I'm obviously not a teacher but I would have thought any school that's got a drug problem is well aware it's got a drug problem. It doesn't need random drug testing to tell it that," Mr Hughill told BBC Radio 5.
David Hart, general secretary of the National Association of Head Teachers, said he agreed with Mr Blair's plans but cautioned they would only work with the support of head teachers.
"Whilst it would be quite wrong for it to be imposed externally, it could be a good example of school-police liaison that helps in the battle against the widespread drug culture amongst our youth," Mr Hart said.
Head teachers will be required to tell all parents if children are being tested at school.
A spokesman for Mr Blair later said the government also wanted more police patrols inside schools, and would be making sniffer dogs available, said the News of the World.
In the same interview - his first since the Hutton report - Mr Blair vowed to stand for a third term in office.