A man will make a case in the Supreme Court for his husband to receive the same death benefits a wife would be entitled to.
John Walker, an ex-employee of chemical company Innospec, is complaining the current arrangements in his defined benefit (DB) scheme mean his husband would only receive a mere 1% of the amount which would be paid to a wife.
A loophole in the 2010 Equality Act means schemes are only required to pay death benefits to same-sex spouses from the introduction of civil partnerships in 2005.
This means partners in same-sex marriages or civil partnerships will potentially lose out on thousands of pounds compared to if they were in a heterosexual relationship.
An employment tribunal had previously ruled in Walker's favour, but a subsequent appeal in an Employment Appeal Tribunal, where Innospec was supported by the Department of Work and Pensions, overturned the decision. The Court of Appeal then rejected a new appeal, so the case has been escalated to the Supreme Court and is expected to be heard in November.
Speaking on the BBC's Victoria Derbyshire Show on 10 August, Walker said: "I worked for this company for 23 years and it didn't matter if I was a man or a woman, if I was gay or straight.
"But because my partner, now my husband, is not a female, he would get a mere £500 or £600, whereas if I was to divorce my husband and marry the first woman that would have me, she would get £50,000 a year. It seems totally unfair and absurd."
Also speaking on the programme, Liberty legal director James Welch said the case could be a pivotal moment in pension law.
"27% of employers are still doing this - there is a statutory basis on which they can do it. It is an inequality that remains in our law and therefore it is very important to change it.
"The government is protecting its legislation. In a sense, it is a bit unfair that we are bringing proceedings against the employer because they are just doing what the law allows them to do."
If the Supreme Court rules in favour of Walker, it could set a legal precedent, allowing same-sex couples across a range of DB schemes to claim higher allowances for their partners. Previous estimates have suggested this could potentially cost schemes around £3bn.
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