Two registrars in south London are being investigated over allegations that they swapped shifts to avoid carrying out civil partnerships for gay couples.

The pair allegedly said they could not officiate the ceremonies because civil partnerships are against their religious beliefs.

The registrars, who have not been named, work at Lambeth Register Office and are said to have informally swapped shifts with other staff.

The Daily Mail reports that the claims came to light during a diversity training session, where a registrar is said to have cited the shift swapping as an example of good practice.

A gay member of staff then complained to the council’s chief executive, Derrick Anderson, and an inquiry is underway.

Liberal Democrat councillor Brian Palmer, who is gay, wrote to Labour council leader Stephen Reed to complain that the alleged practice was “grossly offensive to many members of the borough’s large LGBT community including myself”.

He wrote that the pair were “apparently circumventing Lambeth’s publicly stated equalities standards and the la”.

Mr Reed replied that the council “does not tolerate bigotry” and said that he had asked the council’s chief executive to ensure that all staff members were aware that all services must be provided equally to borough residents.

A Lambeth council spokesman said that no one had been suspended.

He told the Daily Mail: “Lambeth council is fully committed and supportive of civil partnerships.

“The registrars’ service has never declined to administer a civil partnership enquiry, booking, taking of a notice or indeed delivering a ceremony or registration.

“We are very clear that no one has, or ever will in the future, be turned down for a civil partnership for any reason other than that we cannot accommodate the date or time they request.”

In March, an Islington registrar was denied leave to appeal at the Supreme Court after being threatened with the sack in 2007 for refusing to carry out civil partnerships.

Lillian Ladele, a Christian, said her rights had been “trampled” by gay couples but a Court of Appeal judge ruled that exceptions to the law could only rarely be made in a “modern liberal democracy”.