UNISON will not have to rerun its leadership election despite breaches of procedure, a judge has ruled.

Unison general secretary Dave Prentis was re-elected in 2015 with 49.4 per cent of the vote — but all three of his opponents challenged the result with the Certification Officer, alleging that paid union officials had improperly campaigned for Mr Prentis during working hours.

Assistant certification officer Mary Stacey ruled that the union “breached” its election procedures because its “funds, property and resources were impermissibly used to campaign for [Mr Prentis].”

These breaches centred around activities in the union’s London region, where a leaked recording revealed that then-regional secretary Linda Perks had briefed her staff to campaign for Mr Prentis.

But Ms Stacey dismissed a number of other complaints and said there was “no evidence that abuses such as occurred in the Greater London region were occurring in other parts of the country.”

She also concluded there was “no evidence” that Mr Prentis had known of the London region’s activities, and said it would be “disproportionately punitive” to order a rerun.

In the judgement, a copy of which has been seen by the Star, Ms Stacey said Ms Perks used a meeting of officials on October 21 2015 to “campaign for Mr Prentis’s re-election.”

Ms Perks told the officials it was a “lay member briefing,” but Ms Stacey ruled this was “correctly described as a deliberate lie” by the plaintiffs in the legal case.

She also ruled that the union was ultimately responsible for Ms Perks’s breaches.

She said “remarkable clemency and lenience” was offered to Ms Perks in the fact that she was transferred to a job at Unison head office after being disciplined.

Ms Stacey said this is “perhaps not a deterrent penalty to decourager les autres” but that it was not the tip of an “iceberg” and more like a “lilo” — with little to see below the “murky water.”

The judgement also said Unison assistant general secretary Cliff Williams took a “bullying” tone in pressing Electoral Reform Services, the contractor administrating the election, to revise its guidance on election rules.

But it said the pressure applied by union officials did not affect the result.

Ms Stacey branded the “demonisation” of leadership runner-up Heather Wakefield and the “attempted humiliation” of branch secretary Jon Rogers, who reported the leaked recording to ERS, “disappointing.”

She recommends the union drafts “clear, unambiguous and uniformly understood rules” for the role of officials in future elections.

In a statement, the union said: “Unison welcomes the decision of the ACO to uphold the result of the 2015 general secretary election and reject the call from the complainants for a rerun.”