A coroner has found that an appliance brand based in Watford committed "serious errors" after it failed to take prompt action to halt the sale of "defective" gas cookers.

Cornwall Coroner Geraint Williams said that Beko Plc was too slow in withdrawing cookers from sale and contacting people who already bought them after five people died as a result of carbon monoxide poisoning at their homes in 2010 and 2013.

He added that the company which has its home office in Greenhill Crescent, failed to tell trading standards of the extent of the problem and had failed to investigate concerns linked to two other deaths.

Friends and housemates Richard Smith, 30, and Kevin Branton, 34, died in November 2010. In February 2013, John, 90, and Audrey Cook, 86, and their daughter Maureen, 47, also died inside their static caravan.

They all died after accidentally turning on the grill, as uncooked food was found in the oven and their deaths were recorded as an accident.

The grills, manufactured in Turkey by Arcelik had been linked to 18 deaths in the UK and Ireland from carbon monoxide poisoning.

A total of 60,000 Arcelik cookers were affected by the design fault and half were sold in the UK under its Beko brand and the rest by Glen Dimplex.

The inquest heard evidence that Beko, which is Britain’s number one-selling appliance brand, knew the cookers posed a "serious risk" to health but ignored the problem for several weeks. Trading standards was only told of Alexis Landry’s death in Co Cork in January 2009, and it was the following month before the watchdog learned of other fatalities.

Beko was first told by the Irish authorities in November 2008 of the death of Mr Landry earlier that month after using a Glen Dimplex cooker. Arcelik then carried out tests on all its cookers and provided Beko with a list of models that produced excessive carbon monoxide.

In December, the firm learned a coroner was investigating the deaths of pensioners Boris and Vilma Green in Doncaster, two weeks after that of Mr Landry.

Mr Williams said: "Given that the contact was known to be at the behest of a coroner dealing with a fatality, I find as a fact the failure to pursue it by Beko was a serious error

"It is in my opinion undoubtedly the case that an inquiry by Beko would have generated a follow-up call and more details would have been made available.

"Despite the knowledge of the telephone call on December 1 that Mr Landry’s death was now not the only fatality, Beko failed to bring this to the attention of (inspection firm) Intertek or trading standards.

"This also was a serious failing because it meant those two organisations were making decisions based on incomplete information."

Mr Williams said Beko was told of the extent of the problems with the cookers in Ireland and knew it sold similar models in the UK.

Mr Williams said: "I was not given an explanation as to why Beko did not, as soon as those results were known, bring them to the attention of Intertek and trading standards

"In my judgment they had a duty to do so and the failure to do so was a serious one, meaning the two organisations who should have been closely involved were kept in the dark.

"I find as a fact that was a serious failing on the part of Beko. I do accept that Beko began to consider modifying its existing stock of cookers in the way anticipated in Ireland."

A spokesperson for Beko said: "Our sympathies remains with the Branton, Smith and Cook families.

"Since these tragic incidents, we've continued to raise our safety standards and the testing processes our products go through have become even more robust and stringent.

"We also collaborated with the industry to get the UK and EU gas safety standards changed in 2009. The new standard helps prevent a similar tragic event from happening again.

"The cooker models involved in these incidents have been the subjects of a recall for over 10 years and are no longer manufactured or sold. "Our main objective is to ensure that every Beko product is safe for our customers."