London Mayor Boris Johnson is among the Conservatives involved in a new group campaigning for gay marriage in Britain.

The group, announced in a letter to The Sunday Telegraph, includes some of the nation's top Tories, including Michael Gove, the Education Secretary and Patrick McLoughlin, the Transport Secretary.

“Marriage should be open to all, regardless of sexuality. We recognise that civil partnerships were an important step forward in giving legal recognition to same sex couples,” the group wrote. “But civil partnerships are not marriages, which express a particular and universally understood commitment.”

The government is expected next week to announced how it plans to proceed with legislation legalizing such unions.

Johnson wrote in 2001 that he once feared that allowing gays to marry would lead to plural marriages.

“If gay marriage was OK – and I was uncertain on the issue – then I saw no reason why a union should not be consecrated between three men, as well as two men; or indeed three men and a dog,” he said.

(Related: London Mayor Boris Johnson records clip for gay marriage.)