Plans for the Met to have water cannon have found some of their most enthusiastic supporters in Bexley and Bromley, according to a public consultation.

The results of the poll were released on Wednesday as Mayor of London Boris Johnson wrote to Home Secretary Teresa May to voice his backing.

Eighty per cent of respondents from Bexley and Bromley, the highest proportion of all the groups polled, agreed with the statement there was a “gap in the police toolkit which water cannon could fill” in the event of serious public disorder.

But there have been no incidents in either borough in the last five years which would have met the threshold for using water cannon – even during the riots in August 2011.

Seventy-eight per cent of Bromley and Bexley respondents agreed there was a “small, limited role” for water cannon – second only to Havering and Redbridge on 84 per cent.

Erith and Thamesmead MP Teresa Pearce questioned Mr Johnson's backing for water cannon.

She said: "I think that we need to be funding more police officers not a water cannon.

"The Mayor has ignored the responses to his own consultation on this as well as ignoring the detailed assessment published by the London Assembly.

"To be purchasing a water cannon is an unnecessary expense at a time when Safer Neighbourhood Teams are underfunded."

Mr Johnson’s letter to the Home Secretary said: “No one wants to see water cannon deployed routinely on the streets of London.

“It should only ever be used in response to the most extreme cases of public disorder.”

But the Mayor added: “Throughout our consultation in London my team and I and the senior police officers involved have stressed that this tool, if and when licensed, will be ‘rarely seen and rarely used’.”

The final decision now rests with Mrs May. The online consultation polled 4,200 Londoners aged 16 or over between February 18 and March 3.