A landmark legal bid to overturn a public vote and redefine marriage across all 50 states of America began in San Francisco, California, yesterday.

The courtroom trial will centre on a 2008 referendum in which 52 per cent of Californians voted to alter the state constitution to affirm that “only marriage between a man and a woman is valid or recognised”.

Homosexual activists are using the federal court system to argue that the amendment is unlawful under the US Constitution.

The case looks set to go all the way to the US Supreme Court where any decision would apply to all 50 American states.

Brian Brown, director of the National Organisation for Marriage, said the case is an attempt “to put the voters of California on trial and it’s wrong”.

He added: “Our founding fathers would be rolling over in their graves if they heard that the Constitution guarantees the right to redefine marriage. This is absurd.”

Jordan Lorence, one of the lawyers defending the traditional definition of marriage, said the case “potentially could be used to challenge all the state marriage amendments, all the state laws that define marriage as a man and woman, as well as the federal Defense of Marriage Act.”

But supporters of same-sex ‘marriage’ said the traditional definition discriminates against homosexual couples.

In the 31 states where citizens have had the opportunity to vote on the definition of marriage, they have backed the traditional definition on each occasion.

Only five states (Massachusetts, Connecticut, Iowa, New Hampshire and Vermont) have legalised same-sex ‘marriage’ either by court rulings or legislation.

The law changed in Massachusetts, Connecticut, and Iowa following high court decisions. New Hampshire and Vermont legalised same-sex ‘marriage’ as a result of legislation.