Gay rights groups have expressed concern over the appointment of Joel Edwards as one of the commissioners to the new Equality and Human Rights Commission (EHRC).
Edwards, general director of the Christian group Evangelical Alliance, joined the 14-strong team of commissioners already appointed to the body, which was formed in October.
However, Jim Herrick, chairman of the Gay and Lesbian Humanist Association, said that the gay community should be "very afraid" of the appointment, which would put gay rights in danger.
"Joel Edwards leads one of the most homophobic organisations in Britain," he said. "The Evangelical Alliance is an umbrella group that shelters some of the most extreme anti-gay groups and churches in the country.
"How does the government imagine that this man can participate in decisions about the rights of gay people in a fair and balanced way when he believes that we are all sinners who should live without sexual expression?"
The EHRC brought together the three existing UK equality commissions - the Commission for Racial Equality, the Equal Opportunities Commission, and the Disability Rights Commission.
The Evangelical Alliance, formed in 1846, is the largest body serving evangelical Christians in the UK. Earlier this year it launched campaigns against the Sexual Orientation Regulations, which ensure equality for gay, lesbian and bisexual people when accessing goods and services.