But Nick Herbert, the Conservative environment spokesman, leapt on the U-turn as evidence a flagship announcement had quickly turned into a “political dog’s dinner”.

He said: “Labour have dithered for years on this issue and then rushed out a policy consultation weeks before an election which was immediately seen as totally flawed.

“A dog tax on more than 5m owners was proposed last week and is now ruled out by Mr Benn in a humiliating U-turn which just proves how tired and incompetent this government has become.”

The crackdown was ordered after the tragic death of four-year-old John Paul Massey, who was savaged to death by a pitbull in December last year.

John Paul was staying overnight at his grandmother’s house in Wavertree when his uncle’s illegal pitbull terrier lost control and attacked him. He suffered head and neck injuries.

But Jane Kennedy, the Labour MP for Wavertree, suggested a compromise to prevent compulsory insurance for all dogs.

The U-turn leaves the proposal to fit every dog with a microchip, to make it easier to find and destroy dangerous breeds, as the centrepiece of the proposed changes to the 1991 Dangerous Dogs Act.

No changes can be introduced until after the election – and the Conservatives are also opposed to compulsory chips.