Police officers and staff in Northern Ireland involved in a long-running holiday pay claim said they have been vindicated following a Supreme Court judgment.
An appeal by the Police Service of Northern Ireland (PSNI) against a ruling over the backdating of revised holiday pay rates for police staff was dismissed on Wednesday.
A lawyer representing almost 4,000 police officers said the financial cost to the PSNI would be substantial.
The PSNI said it would consider the ruling and how the costs would be met.
Rule changes introduced a number of years ago mean regular overtime worked by civil servants, and other additional payments accrued on top of their basic salary, should be factored in when setting their holiday pay rate.
A cap limiting the retrospective claim-back period in the rest of the UK was not replicated by previous Stormont administrations.
An original industrial tribunal ruled in 2018 in favour of a group representing more than 3,700 PSNI officers and civilian staff that they were owed money for a shortfall in holiday pay dating back 20 years.
The Court of Appeal in Northern Ireland upheld that ruling in 2019.
Lawyers have previously estimated the judgment could cost the police £40 million, and potentially pave the way for similar back payment claims worth hundreds of millions of pounds across the public and private sector in Northern Ireland.
Former PSNI chief constable Simon Byrne appealed the case to the Supreme Court.
The PSNI had accepted the claimants were underpaid and the appeal centred on how far back the claims could reach and the correct method of calculating the underpayments.
But delivering a ruling on Wednesday, Supreme Court judge Lady Rose dismissed the appeal.
She said: “The industrial tribunal held that all of the claimants could rely on the series extension and most, if not all the payments they received, were in a series for that purpose.
“That meant they could claim back over a number of years and not just over the most recent three months.
“The employers unsuccessfully appealed to the Court of Appeal.
“The employers now appeal to the Supreme Court and the Supreme Court unanimously dismisses that appeal.”
Liam Kelly, chairman of the Police Federation for Northern Ireland, said it was a “significant legal milestone” following a seven-year campaign.
He said: “Our men and women should warmly welcome this judgment.
“They have been found to have the same entitlements and protections enjoyed by all workers under employment law.
“At some point in the future, they can look forward to getting what they are rightly owed.”
Mark McAllister, director of employment relations services for the Labour Relations Agency (LRA), said the cost ramifications of the ruling could be “seismic”.
He said: “This is a landmark decision and has very serious public pay and policy ramifications for Northern Ireland.
“As a devolved matter there are different rules regarding holiday pay here as compared to GB and this decision will send shockwaves across a wide range of stakeholders.
“The cost ramifications are seismic.
“When the details of the decision come out, and it becomes clear how far back these holiday pay claims can go, there will be eye-watering sums of money involved.”
Trade union Unison, which led the case on behalf of the police staff in the Supreme Court, said the judgment could affect workers across the UK.
Head of legal at the union Shantha David said: “The previous interpretation meant workers couldn’t get compensation where a series of similar underpayments had happened three or more months apart.
“The Supreme Court understood here that this could allow some employers to game the system by spacing out holiday payments over more than three months.
“For years, many workers have been denied unfairly the chance to have their legitimate claims heard.
“This judgment ensures they’ll get all the wages they’re rightfully owed.”
Niall McMullan, head of employment law at legal firm Edwards & Co, said it was a “resounding and emphatic outcome” for his clients.
He said: “The cost to the PSNI will be substantial.
“Police officers were short-changed when it came to holiday pay and it is now confirmed they are entitled to the same protections and safeguards as other workers.”
Mr McMullan said it will now be for the industrial tribunal to decide how much each officer or staff member should receive.
He added: “This judgment by the Supreme Court is now the end of the line.
“This is a complete vindication and means past under-payments will have to be made good and clients compensated for loss of wages when taking annual leave, but that will be for the industrial tribunal to adjudicate.”
PSNI assistant chief officer for corporate services Mark McNaughten said the force welcomes the clarity the judgment brought to “some complex legal issues”.
He said: “This appeal was progressed in order to seek a definitive ruling from the Supreme Court on difficult points of law and to help ensure that our officers and staff are fairly remunerated in line with our legal obligations.
“We will now take time to study today’s judgment in detail, consider the implications and how the costs will be met.”