Voters in California will have the chance to vote in November on whether to end gay marriage after the state's top court declined to remove an initiative on the issue from the ballot.

California started marrying same-sex couples a month ago after the California Supreme Court ruled that limiting marriage to a man and a woman violated the state's constitution.

Opponents of gay marriage then placed an initiative to amend the constitution on the November ballot. "Proposition 8" declares that marriage will be limited to one man with one woman, reports Reuters.

In the latest phase of a bitter legal battle, supporters of homosexual marriage asked the California Supreme Court to remove the issue from the ballot. The court unanimously denied the petition without detailed comment.

The referendum will appear on the same ballot as the presidential and congressional elections. It requires a simple majority for approval.

"We're disappointed, but this ruling does not affect the campaign against Prop 8 in any way," said a group of organisations fighting for gay rights including the National Center for Lesbian Rights and Lambda Legal.