A lesbian couple travelling from Dublin to Cork were asked to provide proof of their relationship (Envato Elements)

The operator of Ireland’s national railway, Irish Rail, has formally apologised to a married lesbian couple who were asked to prove their marriage was real in order to buy a train ticket.

Mary McNally and her wife Karen Underwood have been together more than two decades and in a civil partnership since 2012. They were married in 2015 as soon as the referendum passed.

As a pensioner, McNally qualifies for free rail travel along with her wife. When buying tickets they “flabbergasted” when a member of staff asked them to show proof that they were an officially married couple – something that is not standard practise for Irish Rail.

“It became an equality issue the minute he asked us for that,” Underwood, an American soul singer, told the Irish Times. “Mary is a different generation to me. I’m 56. I suppose for me because I’m a professional singer I’m in the public eye a lot, plus I’m black.

“Coming from Chicago, I refuse to live a life of oppression for anybody. The minute she was asked for proof of civil partnership – though we are actually married – it became an equality issue.”

McNally and Underwood are convinced that the same question would never be asked of a heterosexual couple.

“If we were a husband and wife would we be scrutinised to the same extent?” Underwood asked. “It’s a knock on your self-esteem and your equality. We don’t carry proof of our marriage in our handbags. We were flabbergasted by what happened.”

After the incident was discussed on local radio station Cork 96FM, Irish Rail issued an official apology and confirmed that “in no circumstances” should a couple be asked to provide such documentation to travel.

“No it is not [standard practice], and we apologise that the customer was asked this,” a spokesperson for the company said in a statement.

“Our booking office staff are required to issue tickets according to the free travel pass validity, which in this instance was two tickets.

“Our revenue protection officers who travel on board may verify directly with the Department of Social Protection that free travel passes are valid and that a person travelling on a spouse/partner ticket is entitled to do so, but in no circumstances should a customer be asked for proof of marriage or civil partnership.”