Whirlpool has admitted the number of its faulty tumble dryers in homes across the country could be far higher than first thought, MPs heard on Tuesday.

Executives from the company told the Business, Energy and Industrial Strategy Committee the true number could be 800,000 and it was working hard to modify those affected.

Last month, the government said it would issue a recall notice for 500,000 dryers that could potentially be a fire risk.

Whirlpool also revealed that in recent years it had logged 54 fires in its tumble dryers and admitted that three of those were models that had already been updated once the fault became apparent.

MPs were taking evidence in relation to a scandal that has seen 1.7 million products modified.

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One witness, Jemma Spurr, a victim whose modified dryer caught fire, told politicians she was asked to sign a non-disclosure agreement about the incident, which MPs said was used for “shutting people up”.

She was given an apology by Whirlpool’s communications chief Jeff Noel. Turning to Ms Spurr, he said: “I apologise to you for whatever distress this situation has caused to you, to your family, to your loved ones and your neighbours.”

Charlie Pugsley, deputy assistant commissioner of the London Fire Brigade, said his teams had seen a wide range of faults causing fires in machines that had already been modified.

And Sue Davies, strategic policy adviser at consumer watchdog Which?, added that a review carried out by the Office for Production Safety and Standards was “completely flawed” because data from Whirlpool had been “incredibly limited”.

Whirlpool representatives were asked by Conservative MP Antoinette Sandbach why some victims were asked to sign NDAs, when the company had previously stated it wanted to raise awareness of the problems to encourage customers to register their products.

She said: “Why is it that you are trying to shut people up by asking them to sign NDAs?”

Mr Noel, from Whirlpool, defended their use, saying they are an “important part” of any settlement.

He was asked several times whether Whirlpool will continue using NDAs over the faulty machines, but declined, saying it was a matter for third party insurers.

He was also asked about the Grenfell tower fire, and whether the company stood by its statement that the blaze, which an expert told a public inquiry is likely to have started in a Whirlpool Hotpoint fridge-freezer, may have been caused by a cigarette.

Mr Noel declined to confirm the company’s earlier statement, saying the matter was for the ongoing inquiry.

He said: “I’m not in a position to say anything other than I think it’s appropriate for issues to have been raised – and I don’t particularly want to ascertain a statement relative to one item that was made by an individual before a legal body.”

Labour MP Vernon Coaker questioned Mr Noel’s decision to not answer the question, by suggesting Whirlpool’s answers appeared to be “about limiting liability” rather than “helping identify the real cause of a fire”.

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A spokeswoman for Whirpool said: “We were pleased to have the opportunity to update the committee on our tumble dryer campaign.

“The Office for Product Safety and Standards (OPSS) recently concluded a comprehensive year-long review of the dryer programme which confirmed that the modification is effective in resolving the issue.

“Safety is always our number one priority and we remain committed to resolving all unmodified dryers affected by this issue. As we updated the committee, we are expanding our recall campaign to include further options to encourage remaining consumers to come forward and remedy their unmodified appliances.

“The crucial message to anyone who still owns an affected dryer and has not already had it modified by Whirlpool is to contact us immediately on 0800 151 0905, or visit Hotpoint, Indesit or Swan‘s safety websites.”

Customers who have had their dryer modified did not need to take any action, the company added.