Lawmakers in Washington state have approved a bill that legalizes same-sex marriage.

The state House approved the measure Wednesday by a vote of 55-43, one week after it was narrowly approved by the state Senate.

Opponents of the bill insisted passage would undermine the conventional institution of marriage as that between a man and a woman. But the bill's chief sponsor, Jamie Pedersen, a gay Democratic lawmaker, argued the word marriage is the one “our society uses to describe committed lifelong relationships.”

The bill was strongly supported by Democratic Governor Christine Gregoire and several prominent businesses based in Washington state, including technology giant Microsoft and the Starbucks coffeehouse chain.

Gregoire will sign the bill into law next week, but it will not officially take effect until early June. However, it could be put on hold if religious conservatives gather enough voter signatures for a ballot measure for the November general election that would repeal the law.

The vote in Washington state came one day after a federal appeals court in California ruled that a 2008 referendum that banned gay marriage in that state was unconstitutional.

Same-sex marriage has also been approved in New York state, Connecticut, Iowa, Massachusetts, New Hampshire and Vermont, as well as Washington, D.C.

Advocates for same-sex marriage are also pushing for similar measures in several other states, such as New Jersey, while voters in Maine could vote on referendum in November.