President Barack Obama must decide whether to repeal the Defence of Marriage Act (DOMA) by June 22nd.

The President, who promised in his election campaign to repeal the controversial law, must respond to a federal lawsuit filed on behalf of eight gay married couples and three surviving spouses in the next four weeks.

The lawsuit was filed by the Gay and Lesbian Advocates and Defenders on behalf of the couples and surviving spouses from Massachusetts, who have been denied legal federal protections available to straight married couples.

DOMA was introduced in 1996 to give states the right not to acknowledge same-sex marriages, even if performed and recognised by another state.

It also bans the federal government from treating same-sex relationships as marriages regardless of whether they are concluded or recognised by one of the states. This means spouses cannot access federal benefits available to straight married couples, such as social security benefits.

According to gay rights advocates, the statute violates the federal government’s promise of equal protection of the laws contained in the Fifth Amendment of the United States Constitution.

DOMA supporters argue that the law protects the right of states to assert their own public policy without the imposition of laws in other states.

President Obama has spoken of his opposition to the law, stating on his campaign website: “[We should] fully repeal the Defense of Marriage Act and enact legislation that would ensure that the 1,100+ federal legal rights and benefits currently provided on the basis of marital status are extended to same-sex couples.”

He has also described it as “an abhorrent law”.

A national grassroots effort, the DOMA Flip Flop campaign, was launched this week to ask the President to repeal the law.

Organisers are asking participants to print out a ‘flip flop card’ with the the statement, “President Obama, please don’t flip flop on DOMA!” on it. Participants are asked to post the ‘flip flop card’ to the White House from now until a decision is made on the lawsuit.

Campaign organiser Paul Sousa said: “President Obama, the defence of this discriminatory and archaic law will be tantamount to nothing short of a flip flop from your previously stated intentions. We’re asking you Mr President, to take a principled stand for equality under the law and be the bold leader that we voted into office.”

Presidents have the authority to not defend a Congressional law that is unconstitutional on its face. Previous presidents who exercised this right include Ronald Reagan in the case of INS v. Chadha (1983) and Bill Clinton in Dickerson v. United States (2000).