Undercover officers trained to spot people carrying out terrorist reconnaissance are being covertly deployed to boost efforts to thwart an atrocity on British soil, the Guardian has learned.

They have been trained in behavioural detection and sent to areas deemed at risk of attack, such as transport hubs and high profile buildings.

A pilot of the scheme detecting suspicious behaviours already claims to have deterred hostile reconnaissance, a precursor to terrorist planning for a potential attack which involves the collection of information so terrorists can maximise the effectiveness of their violent actions. It was later claimed that “chatter” among jihadis was understood to have referred to the incident and confirmed it had been a deterrent.

The scheme was pioneered by City of London police, who guard targets such as the Bank of England and financial institutions. It is being rolled out and will be used around some of Britain’s biggest train stations.

Forces in other urban areas, such as the Metropolitan police which covers most of London, as well as Greater Manchester police, are also studying it.

Police chiefs are also urgently reviewing levels of armed police available to rush to the scene of any attack, with some fearing Britain would struggle to stop the terrorists as quickly as the French did on Friday 13 November. Even then the terrorists killed 130 people and injured scores more.

The fallout from Paris, and its revelation of new tactics by Islamic State, has affected the fresh round of cuts to the police planned by the chancellor, George Osborne, in Wednesday’s spending review.

Police chiefs expect cuts of at least 25%. Those involved directly in the fight against terrorism are expected to be spared cuts, but Mark Rowley, assistant commissioner at Scotland Yard’s counter-terrorism command, and other police chiefs fear neighbourhood officers, vital to gaining intelligence from communities, will be decimated.

On Thursday sections of a letter emerged, written by a police chief, warning that cuts of more than 10% would jeopardise the national security of the United Kingdom.

Spending on the police is the biggest demand on the Home Office budget.

A Home Office spokesperson said it would be up to local police chiefs to decide what they spend their money on and how officers are deployed: “Decisions on wider police funding will not be made until the spending review reports and the operational deployment of resources is a matter for chief constables and police and crime commissioners.”

The City of London police scheme is known as Project Servator.

