One of the lawyers suing says it is a “a real cause for alarm”, but the government says “due diligence” is always taken.
50 million face masks bought by the UK government will not be used in the NHS due to safety concerns.
The personal protective equipment (PPE) ordered from Ayanda Capital have ear loops rather than head loops, and there are concerns over whether they are adequate.
The Good Law Project and EveryDoctor, which are suing the government over the contract taken out because of coronavirus, estimate the masks cost more than £150m.
Court papers show Ayanda was awarded a £252.5m contract on 29 April – with £41.25m payable on commencement to secure the manufacturing capacity.
The firm also supplied 150 million masks of another type, which the government says are unaffected but will be subject to further testing before any are released for use in the NHS.
It also emerged in court papers that the original sales approach came from a businessman called Andrew Mills, who is both an adviser to the UK Board of Trade and a senior board adviser at Ayanda.
Mr Mills told the BBC his position played no part in the award of the contract, the broadcaster reported.
Jolyon Maugham, director of the Good Law Project, said the contract has “revealed a real cause for alarm”.
He questioned: “What other failures remain undiscovered?”
Labour leader Sir Keir Starmer said on a visit to north Wales: “For months we were told that the government was purchasing the right equipment for the front line. Yet again it hasn’t happened.
“There needs now to be an investigation, an inquiry, into what went wrong with this particular contract because it’s just not good enough to people who need that protective equipment that we find ourselves in this position.”
A UK government spokesman said: “Throughout this global pandemic, we have been working tirelessly to deliver PPE to protect people on the front line.
“Over 2.4 billion items have been delivered and more than 30 billion have been ordered from UK-based manufacturers and international partners to provide a continuous supply, which meets the needs of health and social care staff both now and in the future.
“There is a robust process in place to ensure orders are of high quality and meet strict safety standards, with the necessary due diligence undertaken on all government contracts.”
A spokesperson for Ayanda Capital said the company has written to the Times newspaper, which first reported the story, to “correct the assertions made in their article”.
“The masks met all government specifications and standards, the masks are not unusable or unsafe and the government has not wasted any money in purchasing these masks,” they added.
The Welsh government clarified, given health is a devolved matter, that the news does not affect stocks in Wales.
A spokesperson said: “All products sourced during the pandemic were subject to the required regulatory standards and checks were undertaken on all products to ensure such compliance.
“Any PPE products sourced which did not meet the required standards were not considered for purchase and rejected at the assessment/triage stage.”