Theresa May has shelved a decision on whether water cannon can be used on the streets of Britain until after the election , in a major snub to Boris Johnson . Mrs May has refused to sign off the controversial riot control machines despite pressure from the London mayor , who last year spent £220,000 buying three cannon for use in public order emergencies . Home Office sources confirmed last night no ruling on permission would be made this side of the election . That means the machines will lay idle , in a potential embarrassment for the mayor . Boris Johnson spent £220,000 last year buying three water cannon to use in public emergencies , such as the London riots , but Theresa May has today refused to approve their use ( file image ) Soon after buying the three German machines last year , Mr Johnson said it was ‘ highly likely ’ the Home Secretary would sign them off , adding : ‘ My view is we need to get on and equip the police with the water cannon they need , or might need. ’ But in the past she has expressed concerns about whether they fit with the British model of policing and is thought to have concerns about their safety . The standoff over the issue cast light on the ongoing rivalry between the two , both of whom are seen as potential Tory leadership candidates should David Cameron lose the election and step down . Mrs May 's Home Office has been locked in a row with the London Mayor over the decision to buy the machines and whether they fit with UK policing . Last night City Hall sources insisted Mr Johnson had known about the timetable for some time and was ‘ very relaxed ’ about the delay . A spokesman for the Mayor ’ s Office for Policing and Crime defended the decision to purchase the cannon , pointing towards support for them among Londoners . He said : ‘ Independent polling shows that the majority of Londoners support the police having water cannon at their disposal for use in exceptional circumstances . 'The Mayor has made his position clear and awaits the Home Secretary ’ s licensing decision. ’ But critics of cannon warn that in incidents on the continent they have led to serious injury and even death . In one case in Germany a man was blinded and in another a protester was stunned and then killed after being run over . Water cannon have been used in Northern Ireland to quell public order incidents , but never on the UK mainland . Calls for their introduction came during the 2011 riots and later student protests in the capital . Last summer The Prime Minister ’ s spokesman also endorsed their use , saying the prime minister ‘ supports ’ the police ’ s application for water cannon . Mrs May and Mr Johnson two regularly appear at or near the top of polls on who Tories would like as a future leader . She is known to regard the Mayor as a 'faintly ridiculous ' figure . At the time the mayor purchased the machines , he was warned it could be a waste of taxpayers ’ money . When Mr Johnson purchased the machines he said it was 'highly likely ' the Home Secretary would sign off on their use , a political gamble that seems to have backfired . Mr Johnson has previously urged police to get 'medieval ' on rioters , and said officers must never again be left powerless in the face of overwhelming violence like that seen during the riots . But he stressed the chances of the machines being used in the capital , or other mainland cities , remained 'vanishingly rare ' . Police argue water cannon would be useful in a static confrontation where there is a need to create space between police lines and violent crowds . They said it could have helped protect firefighters and paramedics after shops were set ablaze as rioting spread to Croydon in 2011 .
Boris Johnson spent £220,000 on buying three used water cannon last year . Ms May was 'highly likely ' to approve their use , sparking a row . Decision seems to have backfired after Said Home Office refused to sign off on use .