The Washington State Senate has approved a marriage equality bill after an evening debate and a bipartisan vote.

Same-sex marriage advocates knew that 26 Senators, more than the 25 needed, had said publicly that they would support the bill, but in the end 28 voted in favour - 24 Democrats and four Republicans. Twenty-one State Senators opposed the bill, 18 Republicans and three Democrats.

Chief sponsor of the bill and a gay man who’s been in a relationship for 20 years, State Sen. Ed Murray said during the debate: ‘We ask for your support tonight because marriage is the way society says you are family.’

State Sen. Kevin Ranker, who is the son of a gay man said: ‘I am proud to stand on the right side of history and to vote for marriage equality and I am proud to stand for my father.’

One of the four Republicans to support the bill State Sen. Steve Litzow said: ‘I believe an adult should be able to marry the person they love: It’s that simple for me.’

Nearly a dozen amendments were introduced, including several that strengthen legal protections for religious groups and organizations. When the vote was announced there was applause in the packed public gallery. The bill now heads to the House of Representatives where Governor Christine Gregoire has already said she will approve it.

Opponents of the bill have until early June to collect 120,577 valid voters signatures for a referendum on same-sex marriage in November. If that happens, the electorate of Washington state will decide if they want to approve marriage for same-sex partners.

If opponents aren't able to collect enough signatures for a referendum gay and lesbian couples would be able to plan weddings for June. Otherwise, they would have to wait until the results of a November election.