Water cannons, Taser stun guns and CS gas would be valuable to police forces across England and Wales in a bid to avoid a return of last summer's rioting, a review said on Wednesday.

Scotland Yard chiefs said the water cannon crowd dispersal weapon "would have been considered as a tactical option" had it been more readily available in London as violence erupted in August.

Under current arrangements, forces must provide 24 hours' notice before getting water cannon sent over from Northern Ireland.

Top officers are also considering whether Taser stun guns would have better equipped officers to deal with violent disturbances such as the student and Gaza protests.

Several water cannon - worth around £1 million each - could be purchased on a shared basis for forces, the Metropolitan Police's Strategic Review into the Disorder of August 2011 said.

Despite deaths linked to water cannon usage in Northern Ireland, the report says: "Water cannon is widely recognised as an effective tactic to disperse and distance aggressors.

"It requires a precise environment and works most effectively against large static crowds that are, for example, throwing missiles at police, or other communities. It does have tactical limitations, such as manoeuvrability in an urban environment.

"Currently the MPS has no water cannon capability but relies on an agreement with the Police Service of Northern Ireland (PSNI) to have the resource available for use at 24 hours' notice.

"It is the opinion of this review that had it been available for use, it would have been considered as a tactical option during this disorder."

The report added that "it is unlikely to have been an appropriate and practical option owing to the speed and agility of the disorder" but added: "Examples in recent history where the use of this tactic might have been a consideration for commanders had it been available include the Countryside Alliance demonstrations in Parliament Square (2004), the Gaza demonstrations against The Israeli Embassy (2008 and 2009) and potentially the student protests of 2010 where specific locations were targeted.

"In all these cases police had to face significant levels of violence in order to protect key locations and buildings and the staff within them.

"The events of August and subsequent interest in this option have opened the public debate as to whether it is appropriate to have this option more readily available on the UK mainland.

"As such the MPS is contributing to the national discussion and has concluded that water cannons would be valuable in a few rare situations.

"The MPS looks forward to the Home Office resolving its position on licensing and the funding of water cannon as a national asset."
The Association of Chief Police Officers is expected to be in a position to issue guidelines to forces in May, the report said.

"The MPS continues to be involved in discussions regarding the potential purchase of water cannon vehicles to be based regionally in England and Wales," it added.

Chief Constable Ian Learmonth, Acpo's lead on public order, said: "The key for deployment of any tactic is that it must always be justified and proportionate to the situation.

"Large-scale protests constantly challenge and test the police service. No two events are the same and the approaches of protesters and police continually evolve as does the need to review our guidance."

Scotland Yard assistant commissioner Mark Rowley said "we are determined to do all we can to improve" after last summer's "unprecedented" scenes.

"Within the pages of this report are a number of areas the Met can do better," he said, referring to the report.

"The purpose of the review was to identify these and to act upon them - which we are already doing.

"What I hope isn't lost amongst the public's reading of our detailed analysis is the extreme situation and the individual acts of heroism that took place across London. The summer was without precedent and as a result stretched the MPS beyond all anticipated capability. However I accept this will be of little comfort for those who were victim to the violence, looting and arson."