Stephen Frost, director of workplace programmes at the gay rights group, said charities risked drifting into the false belief that their policies were effective. "There is a lot of complacency in the third sector," he said. "Charities often believe that because they do good things everything is fine."
Frost made the comments as Stonewall published its third annual Workplace Equality Index of the top 100 gay-friendly employers. Organisations are ranked according to 20 criteria, including whether they offer benefits to same-sex couples.
Only four charities made the top 100, compared with six last year. The highest voluntary organisation, Nacro, came fifth, ahead of private sector companies such as Lloyds TSB (sixth) and Goldman Sachs (eighth).
IBM took first place, with Staffordshire Police second. The other charities to make the list were St Mungo's (27th), Citizens Advice (42nd) and Barnardo's (51st).
Paul Cavadino, chief executive of Nacro, said his organisation had benefited from its gay-friendly policies. "Gay and lesbian candidates are encouraged to apply for jobs with us, and this increases the chances of retaining staff," he said.