Heterosexual civil partnerships can now take place in the UK, and the first ceremonies took place last week.
The law was changed after the Supreme Court ruled in June 2018 that civil partnerships should not only be available to same-sex couples.
The Government agreed to change the law, and it estimates that around 84,000 mixed-sex couples will become civil partners this year.
Charles Keidan and Rebecca Steinfeld were among the first to enter into a heterosexual civil partnership when the law changed on New Year’s Eve.
They had campaigned for the law to be changed because they wanted an alternative to marriage, which they claim is “patriarchal” and “sexist”.
Now they say civil partnerships could be opened up to include non-romantic relationships.
Steinfeld said they had “helped to create space for deeper discussions about giving legal recognition to other types of personal and caring relationships, such as those between friends, siblings and co-parents”.
Heterosexual civil partnerships have been described as ‘marriage-lite’.
The Christian Institute’s Deputy Director Simon Calvert said: “The problem with heterosexual civil partnerships is that it’s very much a low-commitment alternative to marriage.
“You don’t have to pledge to stay together for the rest of your life, and it’s easier to get out of.
“The gold standard of commitment is marriage, with declarations made in the presence of witnesses and the expectation of lifelong faithfulness”.