The Government is inviting responses to its plans to extend civil partnerships to opposite sex couples.
At present, civil partnerships are restricted to same-sex couples but the Government wants to change the rules so that heterosexual couples can enter into a civil partnership by the end of the year.
The Government is inviting opinions as part of a consultation that is also seeking views on giving existing married couples the "opportunity" to convert their marriages into civil partnerships.
Minister for Women and Equalities, Penny Mordaunt, said: "There are all sorts of reasons why people may choose not to marry, but for a long time it has been the only option for many wanting the legal security it provides.
"Last year the Prime Minister announced government would support the extension of civil partnerships to opposite-sex couples. This is a fantastic step, providing an alternative to marriage for these couples.
"We must now consider those who didn't haven't had this as an option previously, that's why we're consulting on whether opposite-sex married couples can convert their marriages to civil partnerships."
The consultation will run for six weeks until 20 August.
Prime Minister Theresa May announced last October that the Government would change the law to allow straight couples to enter into civil partnerships.
The Scottish Government is moving forward with the same changes and is to introduce legislation to the Scottish Parliament at Holyrood in Edinburgh in the autumn.
The Christian Institute is opposed to the changes and has called heterosexual civil partnerships "another attack on marriage as the gold standard for relationships in society".
Civil partnerships were introduced for same-sex couples in 2004, giving them the same legal rights as married couples.
Ten years later, in 2014, same-sex marriage was legalised in England, Scotland and Wales, giving homosexuals the choice of either marriage or a civil partnership.
The UK Supreme Court ruled last June that civil partnerships should be extended to heterosexual couples following a legal challenge by Rebecca Steinfeld and Charles Keidan, who claimed that the current legal set-up went against their human rights.