Campaigners have rubbished a report which cited the 2004 Countryside Alliance protest in London as a case in which water cannon could have been used.
Chief constables are set to request authorisation to deploy water cannon in mainland Britain for the first time, the paper prepared for the Association of Chief Police Officers (Acpo) and College of Policing says.
The briefing warned that water cannon are likely to be needed by police due to protests triggered by ongoing austerity measures.
But, its claims that the hunting demonstration ten years ago was a scenario during which water cannon would be considered for use, have been scorned.
Westcountry demonstrators were among those to be injured in violent clashes with police outside the House of Commons in September 2004, as they voiced their opposition to the Hunting Bill.
But Tim Bonner, from the Countryside Alliance, said the Metropolitan Police had exaggerated the extent of clashes and the number of officers who had been injured.
“If they are using that as a justification for wheeling water cannon out on the streets of London then you question whether they can be trusted,” he said.
“There needs to be proper consideration of what is deemed to be a threat because I think it would have been complete and utter overkill to have deployed water cannon in that situation.”
Images of blood-soaked protesters provoked outrage at the time and many accused the police of overreacting and being “heavy-handed” after crowds surged towards the Houses of Parliament.
Despite almost 200 complaints, all criminal charges against Met police officers were dropped, or they were found not guilty.
A report by the Independent Police Complaints Commission (IPCC) into the policing of the pro-hunting rally was branded a “whitewash”.
Earlier this month, London Mayor Boris Johnson wrote to Home Secretary Theresa May to say he will ask members of the public and key figures about their views on use of the machines “in the most extreme circumstances”.
While the briefing paper, written by West Mercia chief David Shaw, says it is designed “not to justify why the police service believes that water cannon should be available”, it does go on to explain when Theresa May is likely to be approached for permission.
The paper says: “It is anticipated that the Home Secretary will be approached in early 2014 in respect of water cannon authorisation.”
Water cannon have been used by the Police Service of Northern Ireland for some time, but never by forces on the UK mainland.
The Acpo/College of Policing paper says the Ziegler Wasserwerfer 9000 is likely to be the model of choice, which can get through 9,000 litres in just five minutes if it is running at full pressure. It then takes 10 to 20 minutes to refill from a hydrant depending on the pressure.
A new water cannon costs between £600,000 and £1 million depending on its specification and lasts for 25 to 30 years.
Critics warn the machines can cause serious injuries, such as those reportedly experienced by a German protester who was blinded in 2010.
While deployment of water cannon would be an operational decision for chief officers, Home Secretary authorisation is required before water cannon can be used in England and Wales.
If PCCs and chief constables agree that forces in England and Wales need water cannon, they will need to agree how it should be funded from within their existing budgets.
A Home Office spokesman said: “We are keen to ensure forces have the tools and powers they need to maintain order on our streets.
“We are currently providing advice to the police on the authorisation process as they build the case for the use of water cannon.”