Heather McKenzie secretly ferried cocaine and mobile phones into Shotts Prison in Lanarkshire.

But her illicit scheme was uncovered following a joint investigation by the Scottish Prison Service and Police Scotland who became suspicious about the growing number of drugs found in cells.

McKenzie, 31, of Forth, Lanarkshire, was sentenced at the High Court in Glasgow after pleading guilty last month to charges of supplying a prisoner and others with controlled drugs, phones and a SIM card.

The court heard that intelligence linked serving prison staff to the corrupt supply of controlled drugs and mobile phones to inmates.

During the investigation, McKenzie was identified as a suspected drugs trafficker. Further intelligence suggested she had also formed a close bond with a prisoner serving a life term.

The prisoner’s cell was searched twice and officers found quantities of cocaine and an iPhone, which on examination was found to contain calls and WhatsApp messages to McKenzie’s own mobile.

The court heard that an iPhone can sell for up to £5,000 in prison. Data recovered from the phones revealed McKenzie discussed smuggling drugs into the prison on six separate occasions.

Police officers who carried out a search of her home removed a haul which included £2,500 in cash, syringes, steroids, cocaine and benzocaine, which was recovered from a first aid box in a garden shed.

David Green, procurator fiscal for homicide and major crime, welcomed the sentence.

He said: “The public rightly must have confidence in prison officers to uphold the law. This individual abused her position and fell far short of the standards of professional conduct the public are entitled to expect from members of her profession.

“I hope this sentence sends a strong message to others involved in this kind of criminal behaviour and demonstrates that prosecutors will ensure that people who act otherwise than in accordance with their duties in public office will be brought to justice.”