Labour leadership frontrunner David Miliband has changed his mind on the issue of equal marriage rights.

During an interview with PinkNews.co.uk earlier this month, he said he thought of civil partnerships as being “completely equal” to marriage.

However, a blog on his campaign website now says it is an “anomaly” that committed lesbian and gay couples are not considered married and that removing gender from marriage laws is the “next logical step” for gay equality.

He wrote that the issue of same-sex marriage had been raised repeatedly during recent leadership hustings and conservations with voters.

Mr Miliband, the former foreign secretary, wrote: “It is an anomaly that gay couples – although they can call each other husband or wife – can’t say they are married.

“Canada and Argentina have shown the way forward. That’s why I support calls to change the definition of marriage to include exclusive relationships between couples, regardless of sex. This will mean gay couples will be able to describe themselves as married.”

He added that he supports the amendment to the Equality Act to give churches the option of holding civil partnerships and said the situation would be the same under a new definition of marriage.

“We should not force churches, mosques and synagogues to officiate over gay marriages but equally we shouldn’t stop those who want to,” he added.

Mr Miliband’s spokesman said he has never been opposed to marriage equality but was keen to hear views on the subject.

The coalition government has begun holding meetings on how to allow faiths to hold civil partnerships, although some campaigners are urging ministers to push towards opening up marriage and civil partnerships to both gay and straight couples.

Civil partnerships were designed to offer all the rights and benefits of marriage but a number of gay groups say they are not adequate as they do not receive the respect granted to marriage and are not always recognised abroad.