The mix-up, which took place in 2016, led to two men and a woman having their homes searched and electronic devices seized after investigators linked their broadband connection to the offending material.

The Investigatory Powers Tribunal (IPT) heard that the false allegations had “highly distressing and far-reaching” effects on the trio.

The tribunal ruled that Dyfed-Powys Police had acted lawfully throughout the investigation and that the error stemmed from a technical fault rather than any misconduct by officers.

BT, which has been approached for comment, told the tribunal that two wires inside a street cabinet had been inadvertently crossed, linking two nearby properties.

As a result, the IP address used by the real offender was incorrectly attributed to the first male claimant’s home, which he shared with a friend and his friend’s visiting girlfriend.

All three were granted anonymity by the tribunal, which described the incident as occurring within Dyfed-Powys Police’s “area of operation in Wales” – covering Carmarthenshire, Ceredigion, Pembrokeshire and Powys.

The tribunal heard that the accusations upended the claimants’ lives. Each was forced to disclose the allegations to their employers. The woman was told she could not live alone with her children until she was cleared, while the men were subjected to child protection referrals. One man was placed on restricted duties at work, and the other lost a job offer.

No charges were brought, and police later identified and prosecuted the true offender, who lived nearby.

The tribunal found no grounds for compensation or further remedies, concluding that the police had acted within the law and had taken appropriate steps once the wiring error was discovered.

A spokesperson for Dyfed-Powys Police said: “We recognise the upset and hurt suffered by the claimants in this case, and commend them for the dignity, integrity, and full co-operation shown throughout.

“We welcome the judgement which recognises that the errors discovered were no fault of the police, and all investigatory actions carried out by our officers were lawful, proportionate, and necessary.

“Despite the difficult circumstances, we are satisfied that the party responsible for this error has been brought to justice.”