An appeals court in Michigan has banned public organisations from providing health insurance to partners of gay employees.

The decision has caused outrage amongst American gay rights organisations.

Last Friday Michigan amended its voter-approved ban on gay marriage to incorporate a ruling that prohibits universities and government bodies from recognising same-sex unions in the provision of health benefits. It is the first US state to do so.

America’s largest gay rights group Human Rights Campaign condemned the ruling.

“Today’s vote by the Michigan Court of Appeals is disappointing and sends a chilling reminder of how our families suffer when states enact broad, vague and discriminatory laws,” said HRC’s president Joe Solmonese.

“This decision demonstrates the destructive power of these amendments by unfairly singling out a group of Americans and stripping them and their families of basic protections like health benefits and domestic violence laws,” he added.

The group fears that Michigan-style legislation could become common practice in other states that are hostile to gay rights.

“It really is just a matter of time before we start seeing wholesale litigation in this area,” warned Carrie Evans, state legislative director for the organisation, according to CBS.com.

The Triangle Foundation, a gay rights group based in Michigan, also slammed the decision.

“The Appeals Court could not have gotten it more wrong,” said executive director Jeffrey Montgomery.

“This ruling will result in families being robbed of their health care and other basic necessities that are fundamental to protecting their well-being. This is a tragic ruling.”

Director of Policy for the Triangle Foundation, Sean Kosofsky, accused the Court of Appeals of being out of touch with Michigan’s citizens.

“The vast majority of Michigan’s citizens support domestic partner benefits and did not think they were banning such benefits when they passed 2004′s Proposal 2 [the state's ban on gay marriage],” he said.

Michigan legislates that the marriage of heterosexual partners is “the only agreement recognized as a marriage or similar union,” along with 26 other states.

More than 20 of these have yet to announce whether they will be amending their bans to apply to domestic partner benefits.

In 2005 Alaska courts ruled against any such amendment deeming it unconstitutional to deny domestic partners the benefits that legally married spouses enjoy.

Massachusetts is the only American state that can legally marry same-sex couples. It has been doing so since May 2004.