TRADING Standards bosses are having to scale back on undercover spot-checks at York's shops, because they risk being left open to legal challenge.

City officials carried out no such checks in relation to fireworks and knives last year, amid the concerns.

York's Trading Standards team has for many years used underage volunteers to test whether shops are selling goods such as tobacco, alcohol, fireworks, knives and spray paints to underage customers.

But Matt Boxall, York's Trading Standards Manager, has warned councillors that such undercover work may only be allowed for tobacco or alcohol. Random checks for the other products, and for sun bed sessions, would not be outright unlawful, he said, but they could be open to a challenge under human rights legislation.

In a written report, he said there was a risk fewer routine "test purchases" would now be possible. His warning follows changes in 2012 to the Regulation of Investigatory Powers Act (RIPA), governing how public authorities can carry out surveillance work and investigations.

Councils now need magistrates to okay any work falling under the RIPA remit, but such orders will only be approved for criminal offences worthy of a jail sentence of at least six months, or relating to the sale of alcohol or tobacco to underage customers.

In 2013/14, York's Trading Standards team conducted only 22 tests at shops. They tested 19 for underage alcohol sales, and found one illegal sale. They also tested three shops for underage tobacco sales but found no offenders. The total number of visits has plummeted in recent years, from a high of 341 in 2006/7. Mr Boxall said in his report that the number of illegal sales had generally fallen over the past decade.

His report will be presented next Monday to Cllr Tracey Simpson-Laing, the council's cabinet member for communities. At the same time, she will be asked to approve a Trading Standards plan for the next 12 months, including visiting shops and other premises to give legal advice, carrying out those test purchases with young volunteers that are still permitted, targeted publicity about underage sales and responding to complaints or intelligence from the public, police or other organisations.

On spray paints, Mr Boxall said that intelligence suggested most spray paint used in graffiti was stolen and that the vandalism was by over-16s who could legally buy it anyway.