Eleven British and Irish churches, including the Church of England, the Methodists and the Salvation Army, have formed a new advisory group on ethical investment.
The Church Investors Group will negotiate with companies on their social responsibility records and help members develop ethical investment policies based on Christian principles.
The group has already met with Nestle executives to discuss the company's policy on marketing its baby milk substitute and the employment conditions at its plantations in West Africa.
But chairman John Cunningham, financial secretary of the Roman Catholic Diocese of Plymouth, stressed that it would restrict itself to behind-the-scenes talks.
"We are not a campaigning organisation but a professional investment group and we will listen and work with the management of companies and give them the respect that their professionalism and integrity deserves," he said.
The group, which will formally be launched in January, is based on an informal ecumenical ethical investment network that began in 1973, under the aegis of the Church of England.
"This relaunch of the Church Investors Group shows how seriously the churches take the issue of socially responsible investment," said Cunningham.
"We wish to be proactive and we recognise that, collectively, we carry significant financial and moral weight to promote the socially responsible investment agenda. Additionally, the newly formalised arrangements will make the group more directly participative."
The Church of England has had an ethical investment policy since 1948, but it was not until 2000 that the Church Commissioners decided to sell the Church's arms investments.
"Other denominations are looking to accept their responsibilities in this field and become active partners with the Church of England," said Cunningham.