British Prime Minister David Cameron has given police green light to use water cannon on mainland Britain for the first time as part of a "fightback" against rioters.

Britain's Prime Minister David Cameron gives a statement outside of 10 Downing Street in London August 10, 2011. (Xinhua/Reuters Photo)

After a meeting of the emergency committee Cobra, he said: "Police are already authorised to use baton rounds, and we agreed at Cobra that, while they are not currently needed, we now have in place contingency plans for water cannon to be available at 24 hours' notice."

If water cannons are used they will have to be deployed from Northern Ireland. It would be the first time they have been used on mainland Britain.

The Prime Minister insisted the government would restore order. "We needed a fightback, and a fightback is under way," he said.He said, "Whatever resources the police need, they will get. Whatever tactics the police feel they need to employ, they will have legal backing to do so. We will do whatever is necessary to restore law and order on our streets. Every contingency is being looked at. Nothing is off the table."

Notwithstanding the PM's urgent order for immediate actions, senior police chiefs said these would be ineffectual and the real question was not whether they could cope with the current disturbances, but whether they would be able to deal with similar civil disturbances in future with thousands fewer officers.

David Cameron appeared increasingly isolated last night after senior police officers, MPs and even the Conservative Mayor of London united in a call for him to reconsider police cuts in the face of four days of sustained rioting.

The Mayor of London, Boris Johnson, defied Cameron's position and openly criticised the plan for 20 percent cuts in police budgets.

"The case was always pretty frail and it has been substantially weakened," he said. "This is not a time to think about making substantial cuts in police numbers."

On Tuesday night, riots again hit Britain for the fourth night in succession, with significant violence in the northern industrial city of Manchester and Wolverhampton, as well as minor violence in London.

Police had posted 16,000 officers on the streets of London to prevent a repeat of Monday night's scene of arson, looting, mugging and assaults that took place as hundreds of rioters clashed with police in many parts of the city.

Until now, about 1,000 people have been arrested across the country. (Agencies)

VietNamNet/Xinhuanet