A department estimate shows a 3.7% drop from £856m in 2016/17 to £824m in 2017/18 in resources for the Office for Security and Counter Terrorism.

A Home Office spokesperson said most of reduction in the OSCT estimated budget for 2017/18 refers to “non-counter-terrorism expenditure”.

PF has asked the Home Office what “non-counter-terrorism expenditure” is but the spokesperson said the department could not give "further guidance" at this time.

The figures in a Home Office memorandum on estimated expenditure for next year have been viewed in light of recent concern over police resources.

There is a “small decrease” in resource spending for counter-terrorism police compared with 2016/17 budget, but this is compensated for by an increase in capital funding for 2017/18, the spokesperson added.

He also said the total funding for counter-terrorism police within the OSCT budget is the same in 2017/18 as it was in 2016/17. This does not include additional £32m for armed policing uplift for 2017/2018 that is not in the OSCT budget.

Political wrangling over the number of police officers, which Home Office figures showed dropped by about 20,000 between 2010 and 2016, has arisen following three terrorist attacks in England in under three months.

The prime minister has said a review conducted by MI5 into the handling of the London Bridge terror attack will look at whether lessons can be learned, after it emerged that at least two of the attackers were known to British authorities.

Theresa May also said in a speech on Monday “since 2010 in the face of a growing threat, we have protected the budget for counter-terrorism policing – and increased the resources available to the security and intelligence agencies”.

She added: “We have increased the number of armed police officers, improved cooperation between the police and specialist military units, and provided funding for an additional 1,900 officers at MI5, MI6 and GCHQ.”

MI5 and GCHQ told PF these figures were not publically available to check the figures.

A Conservative spokesman told The Times: “We are increasing cross-government spending on counter-terrorism by more than 30%.

“Of course different budgets across Whitehall move around, but the important number is how much we spent in total to keep Britain safe.”

The 30% rise in counter-terrorism spending was announced in Autumn 2015, when the then chancellor George Osborne promised to spend £3.4bn extra on counter-terrorism – rising to £15.1bn from £11.7bn over the following five years.

Osborne also pledged at that time that the overall police budgets would be protected, rising each year in line with inflation up to 2020.

But this followed a period of austerity measures, which slashed the overall police funding budget, excluding counter-terrorism grants, by 20% between 2010 and 2015.

The OSCT is responsible for terrorism strategy at home and abroad and liaises with the intelligence services and police.

Other figures in the memorandum: