By Gareth Furby and Ed Davey
Millions of metres of dangerous electrical cable may be in homes across the UK, a BBC investigation has found.
In 2010 it was discovered Atlas Kablo, a now-defunct Turkish company, had sold 11 million metres of cable that posed a potential fire risk in the UK.
The Health and Safety Executive decided against a compulsory recall and only seven million metres were recovered.
Critics say more should have been done. The HSE insisted its response was proportionate to the risk.
The British Approvals Service for Cables (Basec) had found the cable had too little copper, meaning it was at risk of overheating.
Chief executive Jeremy Hodge told the BBC: "We identified about seven million metres, which was intercepted and scrapped, which means four million metres or 40,000 reels of cable are still out there.
"It will be tricky to find - most electricians don't keep a record of where cable has gone and there's no requirement to do that."
The unaccounted-for cable was enough to fully rewire 8,000 houses, electrical experts told the BBC.
'Bomb in the system'
Under the Electrical Equipment Safety Regulations (1994) it was within the HSE's power to order a full statutory recall of the cable, forcing retailers to act.
But after Basec raised the alarm, the HSE decided on a voluntary approach, writing to wholesalers and warning them about the product.
It was subsequently found on sale at four branches of Homebase and was still on shelves at the stores as late as 2013, although it is unclear how much of the cable the shops sold.
Sam Gluck, technical manager at electrical fire consultants Tower Electrical Fire and Safety, said this approach had "planted a bomb in the system".
He explained: "If it overheats, it will ignite anything that touches it. If it's against a plasterboard wall that will ignite.
"There should have been an immediate recall and they [shops and electricians] should have been instructed to hand the cables back."
Dr Maurizio Bragagni, chief executive of leading London-based cable manufacturer Tratos, said: "It could be in any shopping centre, any venue, any building."
Of the potential risk of fire, he said: "On a scale of one to 10 it's an eight. I would not like to have this inside my house."
Andy Slaughter MP, a Labour shadow minister for both housing and London, said: "It's extremely alarming. It's revealed that we have inadequacy both in the regulations that are there, and we are not enforcing the ones we have."
He pointed out that both the Grenfell disaster and another fire in his Hammersmith constituency were caused by faulty white goods, and said it was sad that it had taken so many deaths to bring the issue of electrical fire safety into sharp focus.
"This shouldn't have happened. This is cable that's now hidden away in peoples' homes and could be a latent problem for years," he said. "Clearly it should have been recalled. The horse has bolted."
The cable was sheathed in grey plastic and marked with the manufacturer's name. Basec advised that anybody worried about the cable in their home should commission an electrician to test the system.
The BBC has also learned that after the concerns were raised, a three-year sampling programme carried out by the HSE suggested 5% of cable on the market was not up to safety standards.
An HSE spokesman said: "We acted as soon as we became aware of these claims. After the cabling failed independent tests, we worked to ensure that Atlas Kablo took steps to withdraw or recall the cabling from the market voluntarily.
"As a result, many millions of metres of the non-compliant cabling were taken off the market."
He continued: "Following this issue, the Department for Business, Energy and Industrial Strategy funded HSE to carry out a market surveillance project between 2010 and 2012. Most of the tested cabling met the relevant standards.
"HSE reminded distributors of their legal obligations and their liability for trading unsafe products."
A spokeswoman for Homebase said: "The Atlas Kablo cable was withdrawn from sale in 2010, when Homebase was still owned by Home Retail Group.
"Following a full review, Home Retail Group's team of experts deemed the product low-risk, due to the specified usage of the cable for low-voltage items, and did not issue a public product recall.
"Homebase, which was acquired by Bunnings in February 2016, no longer sells this product. The safety of our customers is our number one priority."
The BBC was unable to trace anyone connected with Atlas Kablo to comment.