Tory parliamentary candidates have undergone training by a rightwing group whose leadership has described the NHS as "the biggest waste of money in the UK", claimed global warming is "a scam" and suggested that the waterboarding of prisoners can be justified.

At least 11 prospective Tory candidates, an estimated seven of whom have a reasonable chance of winning their seats, have been delegates or speakers at training conferences run by the Young Britons' Foundation, which claims to have trained 2,500 Conservative party activists.

The YBF chief executive, Donal Blaney, who runs the courses on media training and policy, has called for environmental protesters who trespass to be "shot down" by the police and that Britain should have a US-style liberal firearms policy. In an article on his own website, entitled Scrap the NHS, not just targets, he wrote: "Would it not now be better to say that the NHS – in its current incarnation – is finished?"

Blaney has described the YBF as "a Conservative madrasa" that radicalises young Tories. Programmes have included trips to meet neo-conservative groups in the US and to a shooting range in Virginia to fire submachine guns and assault rifles.

The group's close ties to the Tories were cemented this week when the Conservative party chairman, Eric Pickles, and the shadow defence secretary, Liam Fox, spoke at the annual YBF parliamentary rally at the House of Commons, which was chaired by Blaney.

The links are likely to be deeply embarrassing for the Tory leader, David Cameron, who has pledged to make the NHS his top priority if he becomes prime minister and has attempted to present his party as the choice for green voters. The Conservatives have also talked tough on torture, with the shadow foreign secretary, William Hague, saying torture "helps terrorists justify their hostility to us".

Jon Cruddas, a Labour MP who is heading a campaign against rightwing extremism in the election, said: "It beggars belief that the Conservative party should be so reliant for the training of some of its candidates and thousands of its young activists on an organisation headed by people with such extremist views."

The former deputy prime minister John Prescott said: "Cameron must disown the YBF now. This calls into question whether this organisation reflects the true face of the Tory party."

When asked about their involvement with the YBF, Fox and Pickles both tried to distance themselves from it. Fox, who has spoken at previous YBF events, said: "I am not endorsing them. I was there explaining Conservative party policy on defence. I speak to lots of organisations; it doesn't mean I support them."

Pickles said he did not know about Blaney's views and asked to be sent links to his blog, where many are posted. He subsequently failed to return calls.

Conservative Central Office insists it has no official links with the YBF and does not pay it for its services, but it strongly recommends activists attend Blaney's courses.

Since the YBF's inception in 2003, six other Tory frontbench spokesmen, including the shadow education secretary, Michael Gove, and the shadow arts minister, Ed Vaizey, have addressed YBF events. Former ministers John Redwood and David Davis have spoken at YBF weekend retreats. The group's president, Daniel Hannan, a Conservative MEP, caused outrage last year when he described the NHS to a US television network as a 60-year old mistake.

Writing openly on his own website, Blaney, a Kent-based solicitor, has argued that "humiliation or psychological interrogation techniques are, in my view, not a problem … Waterboarding doesn't do the prisoner any permanent physical harm although he may be reluctant to shower or use a flannel again in the future when/if he is freed."

In October last year, when Greenpeace activists scaled the Palace of Westminster to protest against climate change policy, he called on police to "next time shoot them down … start with water cannon and if that doesn't work, maybe crank it up a level or two".

Last month, the YBF's executive director, London barrister Matthew Richardson, told a major conference of conservative activists in Washington DC that the NHS is "the biggest waste of money in the UK" and in the same speech, he also described global warming as "a scam".

Shortly after the Guardian asked Blaney and the Conservative party to comment on his views, the blog on which they were openly posted was placed behind password protection.

Blaney has stressed the distinction between his personal views and the position of the YBF, which he has said is a broad church open to anyone who believes in the freedom of the individual. He has said that taking students to a firing range was an opportunity for them to experience another culture and that waterboarding is not torture under US law.

It is understood that he considers his remarks calling for police to shoot down green protestors as humour, while on healthcare he has said the NHS should provide free care for those who cannot afford insurance, while everyone else should be privately insured.