Gay couples in Maine hoping to take advantage of this week’s legalisation of gay marriage may be forced to wait months or even a year to hold their ceremonies.

Same-sex marriage opponents in the state have filed a ‘people’s veto’ challenge to the new law.

To get the bill on the ballot in November, they have 90 days to collect 55,000 signatures opposing gay marriage. This means the bill will be put on hold until then. Depending on when petitions are submitted, a referendum may not be held until June 2010.

Governor John Baldacci signed the bill into law on Wednesday after previously voicing his opposition to gay marriage.

In a statement, he said: “I have come to believe that this is a question of fairness and of equal protection under the law, and that a civil union is not equal to civil marriage.”

An umbrella group called the Maine Marriage Coalition is leading the fight to have the bill repealed and is being supported by the National Organization for Marriage, which was instrumental in bringing about Proposition 8, which banned gay marriage in California.

Brian Brown, the executive director of NOM, said: “We will devote staff, volunteers and resources to this battle in Maine. Marriage means a man and a woman, and we will work hard to ensure that voters in Maine have the ability to do what voters in every other state where they have had a chance have done and stand up for marriage as we have always known it.”

Betsy Smith of EqualityMaine, said pro-gay marriage campaigners would fight any attempt to repeal the bill, although she added that fundraising could be an issue in the present economic climate.

She told AP: “Now that it is the law of the state of Maine, we will protect that law.”

The bill had previously been approved by the state’s Senate by 21 votes to 13. It passed in the House of Representatives 89 votes to 57.

The decision made Maine the fifth US state to legalise gay marriage, after Vermont, Connecticut, Massachusetts and Iowa.

Currently, New Hampshire governor John Lynch is deliberating whether to sign a bill legalising gay marriage.

Once it reaches his office, he will have five days to sign it, veto it or decide to let it become law without his signature.

Although he has previously voiced opposition to gay marriage, it is expected that he will be under pressure to allow the measure as a Democrat.