Food inspectors have turned up the heat on city restaurants – after some were found using potentially deadly cooking methods.

The offenders were caught illegally using gas equipment to prepare the popular Indian chapati flatbreads.

Inspectors said the way some chapati flamers were being used could have potentially lethal consequences.

Between last June and December, city council inspectors visited 530 restaurants, takeaways, hotels and guest houses.

More than 54 improvement notices were issued, most as a result of businesses not having adequate arrangements in place to maintain gas equipment in a safe condition.

This included failure to have regular inspections carried out by a suitably competent gas engineers.

But inspectors also served 36 prohibition notices on businesses. These are issued when appliances or fittings have been deemed unsafe.

The notices were handed out to restaurants and takeaways operating chapati flamers, which are used to scorch the top of the popular Indian bread.

A report from Brian Devlin, the council's executive director of land and environmental services, said: "These devices are almost always home-made, with a rubber hose attached to a piece of copper tubing with a flattened end.

"A simple butterfly valve is often the only means of controlling the gas flow and the device is manually lit, for example, by a taper.

"It is then used in a blowtorch fashion to flame the surface of the chapati."

Mr Devlin said the devices do not have an European Commission Declaration Of Conformity and, as a result, are illegal.

Three prohibition notices and an improvement notice were served on a single business on the ground floor of a tenement.

Mr Devlin said: "It had decided to use liquefied petroleum gas or propane to fuel the cooking equipment in the restaurant.

"This is becoming more common as businesses look for ways to cut costs and some gas-fired catering equipment can be dual fuelled."

However, no documentation was available to prove the restaurant's equipment was dual fuelled. Mr Devlin added: "If such equipment is not designed for dual use, the higher flame temperature of propane can damage burner heads, which leads to failure of equipment with potentially catastrophic effect.

"In addition, this business had placed two 46kg (7st 2lb) propane cylinders in the back court area and had fed the supply hoses through an open window.

"These cylinders were unsecured against movement or tampering by unauthorised persons, including children."

Mr Devlin said the restaurant inspections were worthwhile because serious breaches of legislation were found.

He added: "Many of the problems identified were potentially dangerous and this resulted in 10% of the premises inspected being issued with an improvement notice and 7% being issued with a prohibition notice."

Frank McAveety, chairman of the council's sustainability and environment policy development committee, said: "The risks of using gas improperly are generally well known and safety measures are well implemented.

"Unfortunately, we still encounter situations where it is not properly controlled.

"The intervention visits has been a worthwhile exercise in that while serious breaches of legislation were identified, the majority of premises did comply with legislation.