The firm at the centre of the NHS clinical waste scandal has announced it is suing 17 health trusts in Yorkshire which terminated its contracts.
North Lanarkshire-based Healthcare Environmental Services (HES) is seeking “upwards of £15m” in damages.
The company was stripped of the contracts after reports that tonnes of clinical waste piled up at its sites.
The Environment Agency has taken enforcement action against HES and launched a criminal investigation.
Bosses at HES, which has its headquarters in Shotts, have denied claims of mismanagement and insist the company has been unfairly “vilified”.
Managing director Garry Pettigrew said: “We feel that we have been left with no choice but to take legal action against the trusts after the terms of the agreed contracts were broken.
“Our contracts were terminated without first discussing any performance issues with the company and we were given no opportunity to fulfil our obligations.
“We are now taking this action to safeguard the company and our employees’ future, and to give us an opportunity to correct some of the misinformation that has been reported in the media.”
Last month, UK Health Minister Stephen Barclay told Parliament that NHS Improvement had concluded that HES “failed to demonstrate that they were operating within their contractual limits”.
As a result, a number of NHS Trusts in England had served notices to terminate their contracts with the firm, he said.
The contracts it has with more than 30 other trusts in England are still ongoing.
The Environment Agency, which operates in England, previously said HES was in breach of its environmental permits at four of its six sites which deal with clinical waste – by having more waste on site than their permit allows and storing waste inappropriately.
HES has retained its NHS contracts in Scotland.
The Scottish Environment Protection Agency (Sepa) confirmed that it issued enforcement notices at HES sites in Dundee and Shotts in September, where its officers are conducting “ongoing monitoring”.