Mrs Miller said marriage provided the basis for people to "commit to stay together for life" but former education minister Tim Loughton, now a backbench MP, asked why civil partnerships - which have been in place since 2005 - did not provide the same foundation.

BBC: Maria Miller

In fact, taxes are the basis for the second of the two cases concerning same-sex marriage that the Supreme Court will hear this week.

FORBES: Same-Sex Couples and Taxes