A senior aide to the Communities Secretary quit her job after clashes over the new Sexual Orientation Regulations, it has been reported.

Rachel O’Brien left her £50,000 a year post last week. The Mail on Sunday reports that she fell out with Ruth Kelly over gay rights.

The paper also reported that Ms Kelly, the Cabinet minister responsible for gay rights, refused to attend last year’s Euro Pride march in London, and that gay minister Ben Bradshaw was drafted in to attend instead.

Ms O’Brien was appointed as a special adviser on women and equality last year.

She dismissed reports that she resigned after disagreements over gay rights.

“It is complete nonsense. I have never had a disagreement with Ruth Kelly. I left the job for my own personal reasons,” she said.

Prime Minister Tony Blair and Ms Kelly caused outrage in the Labour party earlier this year when it emerged they wanted to grant an opt-out from discrimination legislation to Roman Catholic church-run adoption agencies.

The Sexual Orientation Regulations were due to come into force across the country in January.

They were implemented in Northern Ireland on time, but delayed by the Department of Communities and Local Government because of the amount of submissions received during the consultation period.

The government has repeatedly said that the regulations, which outlaw discrimination against gay, lesbian and bisexual people when accessing goods and services, will be law by April.

The regulations are expected to be published this week, and there is concern that they will grant more concessions to faith-based organisations.

It has already emerged that protections against harassment included in the Northern Ireland regulations will not be in the Great Britain rules.

Tony Blair decided not to give Roman Catholic adoption agencies an exemption from the SOR, but did give them until the end of 2008 to comply with the regulations.

Ms Kelly has been a controversial choice as minister for equality.

The devout Roman Catholic has missed every single gay rights vote since 1997.

When asked if she felt homosexuality was sinful, she refused to answer, saying merely that it is not for politicians to judge the private lives of voters.