UK ministers have confirmed Scotland’s deposit return scheme (DRS) can go ahead but have insisted there is “insufficient justification” for glass bottles to be included.

The UK Government said it would grant the necessary exemption from legislation to allow for DRS to be introduced north of the border from March 2024.

In a letter to First Minister Humza Yousaf, though, it was stressed that including glass in the Scottish scheme could create a “permanent divergence” in the market as schemes planned for other parts of the UK do not include this.

Lorna Slater, the Scottish Government minister responsible for introducing DRS, has promised to update MSPs on the plans as soon as possible.

But her Green Party colleague at Holyrood Mark Ruskell accused the UK Government of “environmental blackmail”.

He accused Westminster of “putting their own narrow party political agenda ahead of our environment and our democracy” – adding this was “utterly shameful”.

Mr Ruskell added: “At least 550 million glass bottles are sold in Scotland every year. Why wouldn’t we include them in a recycling scheme?”

The Green hit out after UK Environment Secretary Therese Coffey, Scottish Secretary Alister Jack and minister for intergovernmental relations Michael Gove said the necessary exemption from the UK Internal Market Act would be granted for a Scottish scheme covering PET plastic bottles and aluminium and steel cans only.

With the Scottish scheme coming in ahead of similar initiatives in the rest of the UK – which are not scheduled to be introduced until 2025 – ministers at Holyrood were forced to seek an exemption from the legislation to deal with the disruption DRS could cause to trade between the four nations of the UK.

In their letter to Mr Yousaf – received by the Scottish First Minister late on Friday – the UK ministers said there had been “strong representations” from both the hospitality sector and distilleries about the impact “on trade and in particular consumer choice created by permanently different arrangements on glass” in different parts of the UK.

The three UK Government ministers said: “Our view is that this type of permanent divergence would be a very significant step for businesses and consumers, and there is insufficient justification for such an approach.”

Mr Yousaf has already claimed it would be a “democratic outrage” for the UK Government to only allow DRS to go ahead without glass.

Regulations passed by Holyrood mean glass bottles, as well as plastic bottles and drinks cans, are currently included in the Scottish Government’s proposed scheme.

The Scottish Government has also noted all but six of the 51 deposit return schemes operating elsewhere in the world include glass, adding that forcing Scotland to remove it from its scheme would mean recycling rates for glass bottles remain at an “unacceptable” 63%.

Mr Yousaf took to Twitter late on Friday to complain that “after spending the day briefing the press, UK Government sent us a letter at 9.45pm tonight”.

He said that letter was “demanding we remove glass from DRS, despite the Scottish Parliament voting for regulations which include glass in the scheme”.

The First Minister added: “That’s your respect agenda for you right there.”

A UK Government spokesperson said on Saturday: “The Government remains unwavering in its commitment to improving the environment while also upholding the UK’s internal market.

“The drinks industry has raised concerns about the Scottish Government’s deposit return scheme differing from plans in the rest of the UK, resulting in the Scottish Government reviewing and pausing their scheme earlier this year.

“We have listened to these concerns and that is why we have accepted the Scottish Government’s request for a UK Internal Market (UKIM) exclusion on a temporary and limited basis to ensure the Scottish Government’s scheme aligns with planned schemes for the rest of the UK.

“Deposit return schemes need to be consistent across the UK and this is the best way to provide a simple and effective system.

“A system with the same rules for the whole UK will increase recycling collection rates and reduce litter – as well as minimise disruption to the drinks industry and ensure simplicity for consumers.”

In light of the UK Government’s stance, the British Soft Drinks Association (BSDA) said the “only viable option now” was for a UK-wide initiative to be launched across all four nations in 2025.

Gavin Pennington, of the BSDA, said its members had “long supported the introduction of an industry-led, interoperable DRS run on a not-for-profit basis to help support a circular economy, reducing litter and increasing recycling”.

He stated: “Our members have made significant investments of money, resource and time since 2019 to prepare for the launch of DRS Scotland.

“However, given the level of political uncertainty currently surrounding DRS Scotland, surely the only viable option now is for all stakeholders to commit to launching DRS across the UK on the same timeframe, October 2025.”

But Dr Kat Jones, director of the Association for the Protection of Rural Scotland (APRS), which has led the campaign for DRS in Scotland, said Westminster’s decision was “in breach of the basic principles of devolution”.

She said: “The Scottish Parliament first considered a deposit system in 2006 because two primary school pupils were upset that one of their dogs got broken glass in its paw. Those former pupils are now nearly 30 years old and we are still no closer to reducing that risk.

“Westminster has decided, in breach of the basic principles of devolution, that Scotland and Wales must endure glass being littered, landfilled and wasted for years to come.

“The Conservatives explicitly promised deposits on glass for England in their last manifesto, making this a particularly perverse decision.”