Former Scottish Green minister Lorna Slater “negligently misrepresented” the likelihood of the government’s deposit return scheme succeeding so as not to lose a key contractor, a court heard.

Ms Slater gave written assurances to waste management firm Biffa that the scheme would go ahead, it was claimed.

However, she failed to say that it would require approval from Westminster under the terms of the Internal Market Act which was set up post-Brexit to ensure no part of the UK operated against the interests of others.

Biffa is said to have relied on personal assurances from Ms Slater when investing in vehicles and equipment to collect recycled items. It is now claiming £166 million from the government in compensation as well as other costs, including lost profit, after the scheme was scrapped.

In the Court of Session on Friday, advocate Roddy Dunlop KC told judge Lord Clark the Scottish Government “negligently misrepresented the assurance it gave” to Biffa.

The company said that Ms Slater, the Greens co-leader and former Minister for Green Skills, Circular Economy and Biodiversity, “made no reference to any outstanding need to seek UK Internal Market Act approval” in order to get the scheme running.

Mr Dunlop said that previous cases of a similar nature had established that Biffa could bring an action against the Scottish Ministers.

On Tuesday, the Scottish Government’s advocate Gerry Moynihan KC told the judge that ministers do not have a “duty of care” to Biffa Waste Services and said the action should be dismissed.

Lord Clark said he will issue his decision into whether Biffa’s case should proceed sometime in the near future.