charlene israel has the story. >> the yeas to the right, 400, the nays to the left, 475. so the yeas have it. >> reporter: it is the first of several votes required for the u.k.'s marriage bill. if it becomes law, the legislation would enable same-sex couples to marry in both civil and religious ceremonies, as long as the religious institution consents. >> today was do we accept the fundamental principle of gay people being allowed to call their union a marriage. i'm glad that we do. >> marriage is a great institution, and it should be there for people who are gay, as well as people who aren't. that's why i have pioneered this change. >> reporter: the vote went cameron's way, but it cost him popularity within his own party. more than half of his 303 conservative lawmakers voted against or abstained from voting for the bill. >> for many people, yes, it is a non-issue. but to a lot of people, they feel this is maybe the straw that has broken the camel's back. >> who are we, who is this government, who is this country to determine and, impose, nationalize a new definition of