An influential network dating back to Mary Whitehouse's Festival of Light looks likely to capitalise on David Cameron's big society

Cliff Richard was a supporter while other luminaries included Mary Whitehouse, Salvation Army leaders and senior clergy. Even Prince Charles sent his "good wishes".

But despite tens of thousands of Christians taking part in September 1971's Nationwide Festival of Light, a month-long campaign against Britain's "moral breakdown" and the permissiveness ushered in by the previous decade, it eventually ran out of steam. After torches and hilltop bonfires were lit around the country, the culmination was a spectacular Trafalgar Square rally.

Exactly 40 years on, however, the Christian network it evolved into is quietly wielding political influence alongside other social conservatives, while gearing up to play an increasingly significant role in the provision of public services under the umbrella of David Cameron's big society agenda.

What's more, the possibility of the first major change to abortion rules for more than 20 years now means it is on the brink of chalking up its most significant victory to date.

An amendment that Tory backbencher Nadine Dorries and Labour's Frank Field have put forward to the health bill would strip abortion providers such as Marie Stopes of their pregnancy counselling roles, opening them up to tenders from "independent" organisations. And now the government has confirmed it will change this key area of the rules anyway.

Bids will almost certainly come from the network of pregnancy counselling centres (CPCs) linked to churches and run by CareConfidential, which became an independent entity in July after spinning off from Christian Action Research and Education (Care). A charity tracing its roots back to the Nationwide Festival of Light, it funds MPs, provides them with interns and has lobbied hard on issues including gay rights, abortion and embryology research.

Other bids could come from the anti-abortion charity Life, which runs its own CPCs and, separately, was appointed by the public health minister, Anne Milton, in May to an expert forum advising the government on sexual health.

Supporters of existing abortion rights and those eager to preserve secularism in public services are, to say the least, rattled, while Labour's frontbench spokeswoman on public health, Diane Abbott, suggests a more profound trend.

"I think that the myriad of encroachment on a women's right to choose that we are currently seeing is best understood in the context of the American phenomenon of so-called 'culture wars'," she said.

"The point for the British politicians pursuing the abortion issue is not just the amendments themselves but that they see it as part of a general approach to politics which has worked so well for the right in America."

As Abbott and others see it, social conservatives in the UK have been borrowing from the tactical playbook of the US Christian right, establishing a network of organisations across a range of fronts and rebranding their traditional "pro-life" language (Dorries and Field's campaign to change the law on abortion is called "right to know").

Certainly, many often-interconnected individuals and organisations pursing a Christian agenda dot the political and legal landscape. Crucially, the Tories now have a strong socially conservative current. David Cameron himself has expressed support for a review of the legal time limit on abortion, as have rising stars of the party such as Louise Mensch.

Of the new crop of Tory MPs elected last year, 12 are members of the Christian Conservative Fellowship (CCF), an influential grouping inside the party. The CCF was founded by MP David Burrowes and the influential blogger and activist Tim Montgomerie, who edits the powerful grassroots Conservative platform ConservativeHome.

MPs from a range of parties also unite on the All-Party Pro-Life Group (APPG). It receives monthly funding from Care, which also (according the most recent register) provides interns for Burrowes and other five other MPs: Sharon Hodgson, Fiona Bruce, Andrew Selous, Gavin Shuker and Gary Streeter.

Beyond parliament, a energetic lobby on issues such as abortion, euthanasia and others exists in the form of groups such as the Christian Medical Fellowship (CMF) and Lawyers Christian Fellowship (LCF).

The latter backed high-profile legal actions taken by Christians such as Lydia Playfoot, the teenager who (unsuccessfully) took a case to the high court alleging that she had been discriminated against when a school banned her from wearing a ring symbolising chastity, associated with the UK offshoot of the US Christian Silver Ring Thing movement. Her case was funded through donations gathered through the LCF's sister group, Christian Concern for our Nation, whose members created Nadine Dorries's website for her 2008 campaign to restrict abortion.

The Silver Ring Thing is also one of the groups on a new umbrella body, the Sex and Relationships Education Council, along with Lovewise, Life, Right to Life and Evaluate (an off-shoot of Care).

Nine parliamentarians attended its launch in May in parliament while the education minister, Michael Gove, sent a message saying he was looking forward to working with the group.

Gove, whose support for faith schools has already endeared him to the Christian right, reminded the launch that the Tories had ensured the Labour government "were stopped when they wanted to remove parents' right to remove children from inappropriate lessons".

Secularist concerns that the big society idea could lead to faith-based groups playing a direct role in provision of sex education were already heightened in April. The Tory-controlled Richmond council awarded a contract for counselling of school-age children to the Catholic Children's Society, which requires its counsellors to "uphold and promote the Catholic ethos of the agency".

Another hub is the Centre for Social Justice (CSJ) thinktank, founded by former Tory leader Iain Duncan Smith and Tim Montgomerie. Although not necessarily faith-based – David Blunkett joined last year – its advisory council includes Field and a key social conservative, Philippa Stroud, who was also involved in its founding.

Formerly the CSJ's executive director, she was appointed as a special adviser to Duncan Smith after he became secretary of state for work and pensions. She was a director at CareConfidential while her husband, David Stroud, is a leading figure in Newfrontiers, an evangelical church network that has played a key role in supporting the Christian charity's network of crisis pregnancy centres.

Montgomerie admits to nervousness at how easily the network of politically engaged Christians could be portrayed as a conspiracy, adding relationships owe more to the "two or three degrees of separation" in politics.

"There isn't a secret meeting where we all plot," he adds, stressing differences between the UK Christian right and its US equivalent.

Faith-communities in the UK, for example, are at a different stage in terms of acceptance of homosexuality, he says, although opposition remains "an article of faith" to many. He emphasises the value UK Christian activists attach to causes such as social justice and international development, rather than focusing entirely on thornier "conscience" issues such as abortion. That said, he casts the "significant" Christian impact on the Tory party as "natural, organic and very real" and a product of 13 years of opposition. He counts Duncan Smith, "a very serious Catholic", as the third most important figure in government.

Montgomerie agrees that a moderation of language and positions by Christian civil society groups has led to the point where they are in position to make the most of the opportunity presented by the big society, or "the opening up of a monopoly".

In some ways, Care and Life exemplify this eschewing of past confrontational tactics for a more discreet approach to influencing public policy.

In other ways they do not. For example, in correspondence between Life and Anne Milton, released to the Guardian under the Freedom of Information Act, Life used language at odds with the conciliatory public words it later used to describe its engagement with pro-choice groups on the sexual health forum.

"We are reducing the amount of abortion. Abortion providers are not. On the contrary, they promote abortion. It is obviously much in their interests to do so. And yet they receive hundreds of millions of taxpayers' money every year," wrote Jack Scarisbrick, Life's chairman.

A former employee at Care meanwhile insists that this "politically savvy" group relentlessly lobbies behind the scenes, drawing up lists of sympathetic MPs and briefings. It views the network of crisis pregnancy centres as being able to give it "the authority" to campaign on abortion.

"People support Care to the tune of a couple of million quid a year and there are individuals who see Care make a difference primarily in parliament. That is their big appeal."

"Their latest tactics are a new development. The have obviously seen an opportunity in the big society."

He adds that while the charity has visibly softened its hardline language over the years, its grassroots are still hugely suspicious of secularism.

"They look back wistfully to a bygone age when the nation was supposedly more Christian and we did have criminalisation of homosexuality, abortion was much more restricted. They do want to turn back the clock."