Mental health campaigners have sounded the alarm over a leaked review of anti-extremism programme Prevent, which suggests those without extremist views are being referred to the programme to access faster mental health services.

Draft extracts of the leaked report by William Shawcross, seen by the Guardian, warn of a “serious misallocation of resources” and that the programme is being misused because of the strain on mental health provision.

“In my assessment, Prevent is carrying the weight for mental health services,” the report says. “Vulnerable people who do not necessarily pose a terrorism risk are being referred to Prevent in order to access other types of much-needed support. This is a serious misallocation of resources and risks diverting attention from the threat itself.”

James Starkie, a former Home Office adviser who founded the No Time To Wait campaign to speed up access to mental health support, said the Home Office must investigate the referrals.

“If people are being referred to the Prevent programme simply to gain mental health support then it needs to stop immediately. These claims in the leaked report should be investigated by government,” he said.

“It cannot be right that people suffering with mental health issues are being labelled extremist simply to access the help they need.”

Other mental health charities also voiced concern. Vicki Nash, the head of policy, campaigns and public affairs at the charity Mind, said: “If true, allegations that some people are being referred to a controversial Home Office-led anti-terrorism programme just so that they can access statutory mental health services are hugely concerning.

“We have to ask ourselves what our nation has come to if the only way to guarantee basic treatment for mental health problems is to be referred to an anti-terrorism programme.”

Alexa Knight, the director of policy and practice at the mental health advice service ReThink, said: “We know that there is huge pressure on mental health services with rising demand and this is very alarming. Like with most health services, it’s really important that people get the right care and the most appropriate care for them and it doesn’t sound as if this is the answer.

“I think the government and all of us need to really understand what is happening here and make sure that there are appropriate routes and services for everybody who needs help.”

A number of community and anti-fascist groups also said they were alarmed at the leaked findings, which also suggested there had been too narrow a focus on Islamist extremism and too broad on rightwing terror.

Shawcross has previously been criticised for comments he made about Muslims as director of the Henry Jackson Society, where he said in 2012 that: “Europe and Islam is one of the greatest, most terrifying problems of our future.”

A former Home Office counter-extremism official, who asked to remain anonymous, said the government would use the number of terror attacks to justify an increased focus on Muslims.

“It’s very shortsighted and suits Shawcross’s agenda,” they said. “The government has been reluctant to look at the definition of ‘Islamist’ itself, which feeds wider anti-Muslim sentiment.” They added that the government had still not responded to Sara Khan’s flagship review into counter-extremism.

Nick Lowles, the chief executive of Hope Not Hate, the UK’s leading antifascism and antiracism campaign group, said the leaked draft was “very worrying” and raised questions about how different forms of extremism could be pitted against each other.

“Prevent, and indeed the wider police approach to violent extremism, should be based on threat and the potential for violence, not pitting one form of extremism against another,” he said.

Zara Mohammed, the secretary general of the Muslim Council of Britain, which has repeatedly raised concerns about Prevent and the role of Shawcross leading the review, said: “Prevent has alienated Muslims and is now being politicised by divisive ideologues keen to frame Muslims as a phantom fifth column. As such, we are not surprised with suggestions that far-right extremism be deprioritised.”