The private member's bill led by Tory MP Tim Loughton is expected to receive government's backing when it gets its second reading in February.
Sir Paul Coleridge, who also founded the Marriage Foundation, told The Sunday Times why he endorsed Loughton's plans.
He explained: "What matters is that people make a decisive, truthful commitment to each other before they enter into a relationship which leads to children."
His comments come as the Equal Civil Partnerships group is supporting a couple challenging the legalities preventing them from entering a heterosexual civil partnership.
Charles Keidan and Rebecca Steinfeld say they don't want to get married, but want legal recognition of their relationship
The couple lost their Court of Appeal bid in February to have civil partnership opened up to them too.
They will have their case heard in the Supreme Court in May.
Currently only homosexual couples in the UK can become civil partners. In other European countries heterosexual civil partnerships exist as an alternative to getting married.
