Dr Steinfeld, 34, told the Guardian: “We are taking this case because the UK government is barring us, and many thousands of opposite-sex couples like us, from the choice of forming a civil partnership, and we want this to change."
Mr Keidan, 39, added that it was time for government to open up civil partnerships to all couples.
The couple were granted permission to continue with their claim by a High Court judge in February 2015.