Grassroots Liberal Democrats are to press for government guarantees that greater involvement from faith-based groups in the provision of public services under the "Big Society" will be subject to strict safeguards to protect secularism and prevent proselytising.

The move comes against the backdrop of recent tie-ups between local government and faith groups. seeking to play a role in provision of services in potentially sensitive areas, such as advising on sexual health.

In east London, a new website aiming to promote sex education for young people "using a faith sensitive approach" has been launched after receiving funding from health authorities. It follows a recent controversy in south-west London over Richmond council's awarding of a £89,000 contract to the Catholic Children's Society, which will be involved in advising pupils on issues including contraception and teenage pregnancy.

Evan Harris, the former Liberal Democrat MP and an increasingly influential voice on behalf of the party's grassroots, is among those involved in pushing to for strict guidelines to govern involvement of faith groups in public services. He said: "The party has made clear that it does not want the government to sanction 'proselytising on the public purse' when local councils or health bodies award a contract to a faith-based group."The Faith, Relationships and Young People (FRYP) website was set up by Alternatives, a charity in Newham which also provides crisis pregnancy counselling and is linked with a national network of independent centres through the Christian organisation, CareConfidential.

A spokesperson for the East London NHS Foundation Trust, which provides services to the City of London and the London Boroughs of Hackney, Tower Hamlets and Newham, said there was a "high level of joint working and partnership work between statutory sexual health services and the charity."

Despite being the focus of suspicion by pro-choice groups and others, Julia Acott, CareConfidential's Counselling Services Manager, insisted they were a fully pro-choice organisation.

She added: "The [FRYP ]website aims to provide young people from faith backgrounds with good quality information about sex and relationships that they may not get in their home or community situations in a way that is sensitive to their backgrounds, and came under the funding scheme's aim of reducing the incidence of sexually transmitted infections in young people."

The website sets out the views of a range of faiths on issues including homosexuality, abortion, contraception and homosexuality although an FAQ section is not working yet.

Newham has consistently had one of the highest rates of teenage pregnancies in the country although it recorded a major drop last year. According to figures released last week, it had the highest rate of abortions in the country – 39.9 per 1,000 women.Harris, vice-chair of the Lib Dem Federal Policy Committee, added: "Any increased use of faith-based organisations delivering essential public services will need stricter safeguards to prevent discrimination against vulnerable and captive populations on the basis of religion or sexuality, as well as to prevent employees needing to pass 'faith tests'.

"The Lib Dems have made clear that religious organisations have as much right as anyone else to provide services, but until legal loop-holes are closed we expect the Government to ensure that contracts contain non-discrimination clauses."