The UK has ended a vaccine supply deal for tens of millions of COVID-19 jabs with French company Valneva, the firm has said.
The pharmaceutical startup's jab candidate VLA2001 uses an inactivated virus similar to flu vaccines.
Some consider it to have the potential to win over people who are cautious about current vaccines from Pfizer and Moderna using new mRNA technology.
The vaccine is being made at Valneva's plant in Scotland and is currently in the third phase of trials. It is not yet approved by regulators.
The UK initially ordered 60 million doses and retained the option for 90 million more. It later added 40 million to its order.
The total value of all 190 million doses is €1.4bn (£1.2bn), Valneva has said.
The UK government "has alleged that the company is in breach of its obligations under the supply agreement, but the company strenuously denies this," Valneva said in a statement.
It did not give further details about the breach of obligations.
"Valneva has worked tirelessly, and to its best efforts, on the collaboration ... including investing significant resources and effort," it added.
The UK government is yet to comment, but Scottish Health Secretary Humza Yousaf said the move was a "blow" for Valneva's site - visited by Prime Minister Boris Johnson back in February.
Shares in the company dropped by 40% following the announcement. But despite the fall, the company's shares are still up by around 50% since the start of 2021.
It said it would still continue its development plan for VLA2001.
"Valneva believes that initial approval for VLA2001 could be granted in late 2021", the company added.
It comes as Boris Johnson is said to be "dead set" on avoiding another lockdown as he prepares to reveal his plan to manage coronavirus over the autumn and winter using vaccinations.
The prime minister is expected to hold a news conference on Tuesday, when he will outline how vaccinations will provide Britain's main defence over the winter months.