A major US multinational oil and gas corporation has said it will offer benefits to legally married same-sex couples across the US for the first time, starting next week.

Exxon Mobil Corp announced on Friday that it plans to begin recognising “all legal marriages”, when deciding eligibility for health care plans for its 77,000 employees and retirees in the US.

The announcement means that as of 1 October, any gay employee who has been married in a state or country where equal marriage is legal, their spouse will be eligible for the benefits.

The company, which faces a same-sex discrimination complaint in Illinois, said on Friday that it was following the lead of the US Government.

“We haven’t changed our eligibility criteria. It has always been to follow the federal definition and it will continue to follow the federal definition,” said Exxon spokesman Alan Jeffers.

Jeffers said the company offers benefits to same-sex couples across 30 countries.

The US Supreme Court in June struck down the Defense of Marriage Act (DOMA), and ruled that civil unions do not provide the same benefits as marriage.

Exxon Mobil Corp is the parent company of Esso and Mobil in the UK.

Last month, the largest retailer in the US, Walmart, announced that it is to offer health insurance benefits to same-sex domestic partners beginning in 2014.