The court ruled in favour of an unmarried woman, Denise Brewster, from Northern Ireland, who was denied access to her late partner's work pension, despite having lived together for ten years and been engaged two days before his death.

Her fiancee Mr McMullan was employed by Translink, a public transport operator, for whom he had worked for approximately 15 years. Throughout that time he had been a member of, and had paid into, the Local Government Pension Scheme.

Ms Brewster argued she was a victim of discrimination and took her case to the highest court. The Judges ruled she was “entitled to receive a survivor’s pension under the scheme”.

Elaine Turtle, director of DP Pensions, said: “This brings occupational schemes into line with the Personal Pension market who have paid out to anyone that is financially dependent with the member on death – so same sex couples have always been able to have lump sum death benefits. I am surprised it has taken so long for these types of schemes to move with the times.”

Greg Kingston, head of communications, product & insight, Suffolk Life said: “This ruling will likely extend the assumed liabilities of these schemes and put them under greater financial pressure.

“The UK's public sector pension liability current sits at around £1.5 trillion, and public sector pensions currently in payment cost every UK household around £1,000 every year - equivalent to 1.6% of GDP - and the cost is growing. It simply isn't sustainable.”

Former Pensions Minister Steve Webb, director of Policy at Royal London, said: “This is a very welcome ruling. It is totally unacceptable for cohabiting couples to be treated as second class citizens. With more than six million people living together as couples and the numbers rising every year, this is an issue that needs to be addressed as a matter of urgency. We need pension scheme rules which reflect the world we live in today, and not the world of fifty years ago”.

Claire Trott, head of pensions strategy, Technical Connection, said: "This ruling will hopefully mean that schemes will look into their rules to try and avoid discriminating against those that don’t feel the need to get married.

“This particular example seemed pedantic because it was only the lack of a nomination form that meant that payments weren’t made, Ms Brewster met all the other requirements of the scheme, such as time co-habiting. These requirements again would not have needed to be met if she had married her long term partner and she wouldn’t actually have even needed to be co-habiting should they have been married.

“It seems amazing in this day and age, where marriage is often delayed by those saving for a house together or co-habiting for extended periods of time for other personal or other financial reasons, to be discriminated against when it comes to pensions.”

Andrew Pennie, head of pathways, at Intelligent Pensions said: “We don’t believe the supreme court ruling will have major implications going forward. Regulations already give unmarried partners rights under the scheme. In Northern Ireland there was an additional requirement to complete a nomination form and the judges have rightly concluded the commitment demonstrated by living together for ten years far outweighs the commitment required to complete a pension nomination form.

“Private sector schemes usually pay dependant's pensions at 'trustees' discretion', so not affected by the ruling. A Local Government scheme is governed by statute, not trust deed and rules.

“It is pleasing the Judges have backed the legislation as it was intended and have delivered this outcome but it is disappointing it has taken almost seven years for Ms Brewster to win her case.”