This judgment should cause both McKenzie friends and those who use them to stop and think.

An unqualified legal adviser has been ordered to pay more than £260,000 in compensation after he caused a man to miss out on damages and incur huge costs in a medical negligence case.

A High Court judge said that the adviser, who held himself out as a competent legal professional, owed a duty of care to the 70-year-old man, despite not being legally qualified.

It is the first time that the High Court has ruled on the duty owed to the public by unqualified advisers, known as McKenzie friends. They can assist people who are not represented by a solicitor or barrister in a court of law by prompting, taking notes and giving advice. They need not be legally trained or have any professional legal qualifications. Their numbers have grown after cuts to legal aid left many people unable to afford lawyers.

Recently the lord chief justice said that he was “deeply concerned” by the growth in the number of McKenzie friends, who are unregulated, unqualified and uninsured.

In the case on Friday Paul Wright, a nurse and care home manager from Essex, suffered permanent disability after three plastic bags were left inside him during an operation in 2004 at the Basildon and Thurrock NHS Foundation Trust. The court ruled that as a result of negligent advice from George Rusz and his company, Troy Lucas, Mr Wright had been able to pursue only part of a claim against the trust.

In 2011 the trust admitted limited liability and settled the claim for £20,000. Mr Wright had to pay £75,000 towards the hospital’s legal costs because, the court said, of the way that Mr Rusz had conducted the case. According to the High Court ruling Mr Rusz had made spurious applications for disclosure from the hospital and failed to comply with court orders. He also failed to take advice from a barrister and sought “fantastical” sums for damages ranging from £1 million to £3 million without submitting evidence to support the figures.

The judge said that on the “most charitable” reading he was “out of depth”, but at worst he had “set out on obtaining the maximum amount of money”. The High Court ordered Mr Rusz to pay £263,759 to Mr Wright, plus £73,200 costs.

The judge said that the compensation was what Mr Wright was likely to have received had he settled his complete case against the hospital.

Mr Rusz said that he had a law degree from the Open University but no other legal qualifications.

Judge Jennifer Eady, QC, said that he had been careful not to describe himself as a solicitor, but as an “experienced legal professional”. As such the judge said that he owed his client a duty of care to advise him to an appropriate standard. She ruled that his advice fell short of that standard and had at times been “positively harmful”.

This month Lord Burnett of Maldon, the lord chief justice, said that it was for parliament to introduce a ban on McKenzie friends charging for their services.

Lucy Frazer, QC, a justice minister, said recently that the issue was something that the ministry should look into.

Emma Jones, a partner at Leigh Day, the law firm that represented Mr Wright, said: “This case highlights the dangers of allowing individuals to offer legal services whether as a litigation company or Mackenzie friend without having to be regulated or insured.”

Mr Wright told The Times: “If I had been able to access legal aid and enlist a professional solicitors firm I would have had my compensation many years ago, which would have improved my quality of life and that of my family who care for me.”

Mr Rusz, who represented himself, had denied any liability, saying that there had been no contract between him and Mr Wright and that he therefore owed him no duty of care.