Boris Johnson’s inflammatory bid to flood London with “extremely dangerous” water cannon was doused by the Home Secretary yesterday amid a public outcry over safety.

The Tory mayor has already blown £218,000 of public money on purchasing second-hand water cannon for the Met.

Campaigners have warned of their danger after a German man was blinded after being hit by a water cannon during a protest in Stuttgart in 2010.

Three 23-year-old machines, unwanted by the German police, were shipped to Britain last July.

Top cops claim they need the weapons to control crowds and say they would have unleashed them against students protesting against tuition fees in 2010.

In an act of bravado designed to dispel safety fears Mr Johnson offered to be blasted himself by one of the high-pressure jet streams.

But Ms May has refused to sign-off their use in her final two months as a minister, meaning the cannon may never be deployed on the streets of Britain.

A Home Office spokesman confirmed that no decision will be made this side of the election.

Labour London Assembly crime spokeswoman Joanne McCartney said it “should be a clear signal to Boris Johnson that he is the only one who thinks this ill-judged proposal is a good idea.”

Ms May’s decision could spark a civil war between the two Tory leadership rivals just eight weeks before the general election.

It comes after the London Assembly police and crime committee rejected “contradictory” claims by senior police about why they needed water cannon.

Ms McCartney, who chairs the committee, said yesterday that Mr Johnson should admit he was wrong and sell the cannon to free up cash for the stretched Met.

“Water cannon are not only extremely dangerous, they are bluntly indiscriminate tools which should have no place in our capital city.

“If he refuses (to sell), the public will undoubtedly conclude that he is more interested in continuing his militant posturing than doing what is best for the capital.”

The Met Police did not provide a response to the Star’s request for comment.