Three gay couples are suing the state of Alaska for denying them equality in tax laws.

They claim that the state’s tax assessment laws discriminate against same-sex couples by denying them equal access to a property tax exemption for senior citizens and disabled veterans.

Individuals who qualify for the tax exemption but live with same-sex partners are only permitted to, at most, half of the exemption available to heterosexual married couples.

The American Civil Liberties Union (ACLU) of Alaska, which has filed a lawsuit on behalf of the couples, says that they are being treated like roommates instead of families.

Tom Stenson, from the legal equality group, said: “Alaska law is clear that denying committed same-sex couples the same rights as married opposite-sex couples is unconstitutional.

“For senior couples and disabled vets, every bit of savings counts. These couples should not have to pay more taxes than other families.”

One of the plaintiffs in the case, Julie Vollick, served in the US Air Force for 20 years and now has service-related disabilities. She has four children with her partner Susan Bernard.

Ms Vollick said: “I was proud to serve our country and defend our democratic values. All we want is the fairness I’ve fought to defend.”

Alaska does not recognise same-sex marriage or civil unions but the ACLU argues this is a constitutional issue.

A 2005 ruling by the Alaska Supreme Court found that denying gay couples equal rights violates the state’s constitution. The ACLU says it has asked the state twice in the last year to resolve the property tax exemption without litigation.

Roger Leishman of Davis Wright Tremaine, which is working with the ACLU, said: “We have tried to resolve this issue with the state out of court with no success. We’re hopeful that the courts will rule on the side of fairness.”