The following correction was printed in the Observer's For the record column, Sunday 9 May 2010

The founder of the controversial US private security firm Blackwater, which funds a US Christian group called the Alliance Defence Fund, is Erik Prince, not Erik Prinze.

Gordon Brown may be a son of the manse, but, when it comes to evangelical Christianity, David Cameron's Conservatives have been busily amassing powerful, wealthy and influential supporters.

An analysis of the Tories' accounts reveals that a string of powerful Christian businessmen are helping bankroll the party, with many making significant donations in the days after the election campaign started.

Former investment banker Ken Costa, who gave £50,000 last month, is the chairman of Alpha International, an organisation that promotes the hugely popular Alpha course that has introduced millions of people to Christianity.

Michael Farmer, who founded a metals brokerage, gave £250,000 last month and has donated similar sums several times in the past. A self-made multi-millionaire, Farmer says he is happy to carry the "God squad" label. In a recent interview, he explained that he was backing the Tories because Labour "has governed incredibly badly".

"The tax and benefits structures put in place under Labour have not created a strong society; they've done the opposite," he said. "They've just encouraged unhappy lives. The core unit of society – husband, wife, parents, children – has been dismantled. Labour's idea of a family is three people who share a fridge."

It is perhaps not surprising to learn that Farmer has also donated £2,000 to Philippa Stroud's campaign to become Tory MP for Sutton & Cheam. Like her political ally, Nadine Dorries, the Tory MP for Mid-Bedfordshire, Stroud is one of growing band of Tories happy to wear their faith on their sleeves. She once explained that it was "massively important" for Christians to engage in politics because "we have a unique understanding of the value of human beings".

As head of the influential Centre for Social Justice (CSJ), a Christian-orientated thinktank set up by former Tory leader Iain Duncan Smith, Stroud has had a profound effect on the party's approach to social issues.

The CSJ claims to have been responsible for formulating some 70 Tory policies. David Cameron's controversial tax breaks for married couples owes much to its thinking.

The rise of the Christian Conservatives is viewed by some in the party with a mixture of suspicion and fear. The Conservative Christian Fellowship, an increasingly powerful grass roots organisation set up by one-time Exeter University student Tim Montgomerie – who now runs the influential ConservativeHome website – counts no fewer than 37 prospective Tory candidates as members. Its chairman is David Burrowes, the shadow justice minister who was at Exeter with Montgomerie.

The organisation claims it "faciliates meetings between the Christian community and the party on various policy areas such as education, international development, home affairs and community cohesion".

It is unashamedly conservative on social issues, especially the importance of the family. "If Christians want to support marriage, they can do so very practically in 2010, by voting Conservative," said Elizabeth Berridge, the CCF's executive director.

Nor is it afraid to show its teeth. Earlier this month, Philip Lardner, the Conservative candidate for North Ayrshire and Arran, was suspended after writing on his website that homosexuality was "not normal".

Montgomerie was quick to respond, describing the suspension as "disproportionate " and saying Lardner's views were shared "by many conservative Christians and people of other faiths"

Some have detected the influence of the Christian wing of the Tory party in recent announcements from Cameron. Asked whether he would press for a reduction in the abortion limit, Cameron said there should be a review. "I think that the way medical science and technology have developed in the past few decades does mean that an upper limit of 20 or 22 weeks would be sensible," he told the Catholic Herald in an interview in which he also strongly endorsed faith schools.

Lowering the abortion limit is one of the key aims of Dorries who, as the New Statesman discovered, has received support and briefings from Christian Concern For Our Nation. The little known but well organised group claims it "exists to serve the Church by providing information to enable Christians to stand up publicly against a tide of unchristian legal and political changes in the United Kingdom". Accounts reveal it received more than £265,000 in gifts and donations last year.

Its sister organisation, the Christian Legal Centre, backed the case of Gary McFarlane, the relationships counsellor, who was sacked by the Relate Relationship organisation after he refused to provide sexual counselling to homosexual couples because of his Christian beliefs, and of Nadia Eweida, the BA employee who was prevented from wearing a small cross on her necklace.

The CLC runs a number of initiatives with the Alliance Defence Fund, a hugely powerful US Christian group that sponsors many Republican politicians and holds a "Day of Truth" in US cities to show "that God created our sexuality to be expressed between a man and a woman married to one another."

One of the ADF's biggest donors is Erik Prinze, founder of the highly controversial US private security firm, Blackwater, now the subject of lawsuits over the actions of its employees in Iraq.

Earlier this year, CLC and ADF supporters met at Exeter College, Oxford, to discuss how British Christians could answer the "call of today's worshipful warrior". It seems that for an increasing number, the answer is to be found in Westminster.