Some 400,000 surgical gowns ordered from Turkey do not meet British safety standards, the UK government has said.
Up to half of the personal protective equipment (PPE) order was flown to the UK by the RAF last month, but has not been given to NHS workers and is now stuck in a warehouse.
The prime minister’s spokesperson said the NHS was speaking to the supplier about getting replacement gowns.
They said if replacements were not possible it would seek a refund.
But speaking earlier on Thursday morning, a spokesman for the Turkish company which supplied the goods said they had not received any complaints.
Mehmet Duzen, from Selegna Tekstil, told the BBC the company had not had any communication from the NHS, the British embassy in Ankara, or British government officials complaining about the quality of its gowns.
“The fabric we supplied was certified. All the goods were certified,” he said, adding that they were ready to respond if there was a mistake.
The Department of Health said it was working “night and day to source PPE”.
During the past few months as the UK has tackled the coronavirus pandemic, healthcare workers including doctors and nurses have complained of a lack of adequate kit such as gowns, masks and gloves.
PPE is essential for protecting front-line workers exposed to Covid-19, and without it workers are concerned they could catch or spread the virus.
Amid a row over the procurement of PPE in April, the government announced it had managed to source a large supply from Turkey.
After several delays, the RAF was deployed to Istanbul to fly it back to RAF Brize Norton on 22 April.
It is not known how much PPE was on board but the aircraft which was used can carry about 40 tons of cargo, about half of the consignment.
But now the government has confirmed that all of the surgical gowns that were delivered were unusable because they did not meet the required criteria – as was first reported by the Daily Telegraph.
The chief executive of the NHS Confederation, representing health and care leaders, said the shipment from Turkey had been “sizeable” but had only offered a few days supply.
Niall Dickson told the BBC Radio 4’s Today programme that NHS bosses understood that the quality of equipment was “not always what it says in the box” but warned that making promises that are not kept “undermines confidence” in the government among frontline staff.
He added that supplies were now “generally better” in hospital but that care homes and GP surgeries still face “some difficulties”.
One paramedic, who wanted to remain anonymous, described the PPE shortage as like sending soldiers to fight in a war without guns.
“We are desperately short of gowns,” he told BBC Radio 5 Live. “We have got enough aprons – which dinner ladies would use – but the actual gowns, we are definitely short of those.
“You’re walking through the door, you’re hearing these poor souls coughing and spluttering, and you’re thinking, ‘am I going to be catching that and taking it home to my wife and kids?’,” he said. “It’s absolutely terrifying.”
Last week, the Department of Health asked hospitals not to order their own PPE but to to rely on the government’s national procurement scheme.
But Mr Dickson warned that further delivery problems would encourage some NHS organisations to continue to place their own orders.
Asked about the order from Turkey, Northern Ireland Secretary Brandon Lewis said it was “reassuring” that British experts were “ensuring the best quality of equipment”.
He told BBC Breakfast that the government was “working through” a list of about 10,000 UK-based firms which have offered to make PPE, and had received 250,000 gowns from Northern Ireland.
In a statement, the Department of Health and Social Care said there were shortages of PPE around the world, not just in the UK.
“We are working night and day to source PPE internationally and domestically and brought together the NHS, industry and the armed forces to create a comprehensive PPE distribution network to deliver critical supplies to the frontline,” a spokesperson said.
“All deliveries of PPE are checked to ensure the equipment meets the safety and quality standards our frontline staff need. If equipment does not meet our specifications or pass our quality assurance processes it is not distributed to the front line.”