California has voted to ban gay marriages only months after the practice was legalised, in a move which left thousands of homosexual couples stranded in a legal limbo.

The proposal to limit marriage to members of the opposite sex was approved by 52.1 percent of voters, compared with 47.9 percent who voted against, with 95 per cent of votes counted.

The referendum, known as Proposition 8, called for the California constitution to be amended by adding the phrase that: “Only marriage between a man and a woman is valid or recognised in California."

The plan, for which groups voted at the same time as for the president, was viewed by Conservatives as the people’s way of overturning the state Supreme Court’s ruling in May that legalised gay marriage.

The court’s ruling had overturned an earlier plebiscite in 2000 when 61 percent of voters agreed marriage should be defined as being between a man and a woman.

The result leaves thousands of gay couples in a legal limbo after they rushed to get married in California since June. They include some celebrity marriages.

Hollywood stars including Brad Pitt and Steven Spielberg as well as multinational companies such as Apple had flocked to the camp opposing the ban, with donations of up to $100,000. But supporters unleashed a flood of hard-hitting ads especially targeting the Hispanic community and its traditional Christian and family values.

The proposed ban had 5,125,752 votes, or 52 per cent, while there were 4,725,313 votes, or 48 per cent, opposed. Similar bans had prevailed in 27 states before yesterday's elections.

Some in San Francisco vowed to continue fighting for the right to marry if the proposition does pass. “My view of America is different today,” said Diallo Grant, a gay man with mixed-race parents. “The culture wars will continue.”

Elsewhere, voters in Colorado and South Dakota rejected measures that could have led to sweeping bans of abortion, and Washington became only the second state - after Oregon - to offer terminally ill people the option of physician-assisted suicide.

A first-of-its-kind measure in Colorado, which was defeated soundly, would have defined life as beginning at conception. Its opponents said the proposal could lead to the outlawing of some types of birth control as well as abortion.

The South Dakota measure would have banned abortions except in cases of rape, incest and serious health threat to the mother. A tougher version, without the rape and incest exceptions, lost in 2006. Anti-abortion activists thought the modifications would win approval, but the margin of defeat was similar, about 55 per cent to 45 per cent of the vote.

“The lesson here is that Americans, in states across the country, clearly support women’s ability to access abortion care without government interference,” said Vicki Saporta, president of the National Abortion Federation.

In Washington, voters gave solid approval to an initiative modeled after Oregon’s “Death with Dignity" law, which allows a terminally ill person to be prescribed lethal medication they can administer to themselves. Since Oregon’s law took effect in 1997, more than 340 people - mostly cancer sufferers - have used it to end their lives.

Elsewhere, the marijuana reform movement won two prized victories, with Massachusetts voters decriminalising possession of small amounts of the drug and Michigan joining 12 other states in allowing use of pot for medical purposes. Henceforth, people caught in Massachusetts with an ounce or less of pot will no longer face criminal penalties.

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