Green minister Lorna Slater is facing fresh criticism after a scathing report by MSPs branded part of her latest project “entirely unrealistic” and cast doubt on its “financial credibility”.

Holyrood’s Finance Committee said the Circular Economy Bill currently being steered by Ms Slater may breach the parliament’s own rules on providing “best estimates” on costs. 

It said MSPs would have to decide “whether the outcomes it seeks to deliver outweigh any financial or affordability considerations” when they vote on its general principles in January.

It also criticised the Scottish Government’s growing use of such “framework bills”, which create new powers but fail to explain how much they will ultimately cost. 

The cross-party committee said such legislation “undermines parliamentary scrutiny” and risked Holyrood passing laws which could lead to “significant” unforeseen costs.

“We consider that the increased use of framework bills, with no clear identification of the estimated costs of implementation, poses long-term risks to the Scottish Budget, both now and for successive governments,” it said.

It said the Bill’s financial memorandum (FM), which sets out likely costs, was inadequate and needed “much greater detail” and asked for six-monthly updates from Ms Slater.

“The Committee is not convinced that the FM in its present form meets the requirements set out in the Parliament’s Standing Orders to provide ‘best estimates of the costs, savings, and changes to revenues to which the provisions of the Bill would give rise’,” it said.

The seven-member committee, which includes Green MSP Ross Greer and three SNP MSPs, was unanimous in its findings.

The report is another blow to Ms Slater’s reputation at Holyrood. 

The co-leader of the Scottish Greens, who is minister for the Circularity Economy, has already seen her deposit return scheme fall apart. 

The Circular Economy Bill is intended to boost recycling and reduce littering through better local waste services, fines for littering and flytipping and a disposable drinks cup levy.

The FM assumes that 100% of people who get an £80 fine for throwing litter from cars will pay it, despite evidence from councils that only around 15% of litter fines are paid. 

The committee said the 100% payment rate assumption was “entirely unrealistic”, and so the projected income could not be used to off-set enforcement costs.

“We consider this approach to identifying savings to be unsatisfactory,” it said.

The committee’s SNP convener Kenneth Gibson said the Bill fuelled concerns that “affordability does not appear to be a key factor in Scottish Government decision-making”. 

He also said Ms Slater’s vow to consult on the cost of minor, secondary legislation arising from the Bill was no substitute for assessing its affordability at the outset.

He added: “Our committee is not convinced that this Bill’s financial memorandum meets the requirements set out in Parliament’s Standing Orders to provide: ‘best estimates of the costs, savings, and changes to revenues to which the provisions of the Bill would give rise’.

“We’ve seen an increasing use of ‘framework’ bills that provide government with future enabling powers. These do not, however, provide best estimates of all likely costs, and undermine parliamentary scrutiny.  It also risks the Parliament passing legislation which may in the end - once outcomes are fully understood – lead to significant cost increases.

“The increased use of framework bills with no clear implementation costs, poses a long-term risk to the Scottish Budget, both now and for successive governments.”

Mr Gibson said the committee was “disappointed” that Scottish Ministers had not yet delivered on “the level of financial data, clarity and transparency required”.

The MSPs have asked Ms Slater to deliver twice-yearly updates on expenditure incurred to date, changes in forecast costs and savings, and relevant secondary legislation, until all provisions of the new law are operational, assuming it is passed.

Tory MSP Liz Smith said: “Yet again, this is a damning verdict from the Scottish Parliament’s finance committee on key legislation being brought forward by the SNP-Green government.

“The complete lack of financial transparency on the Circular Economy Bill shows Lorna Slater has clearly not learned any lessons from her shambolic handling of Scotland’s deposit return scheme.

“Lorna Slater cannot pass the buck and hide from serious questions being raised over this bill. She must ensure she responds to this report as a matter of urgency.”

Liberal Democrat MSP Willie Rennie added: "Even supporters of this Bill can recognise that simply allowing the government to press ahead with fudged numbers is a recipe for disaster. 

"Lorna Slater has been responsible for a series of proposals which have been half-baked at best. If the Finance committee sigh every time they see her name attached to a piece of legislation, just imagine how the businesses and stakeholders who have to deal with the consequences feel." 

Labour MSP Michael Marra said: “This damning report further reveals how the SNP have made such an unholy mess of managing taxpayer’s money. “Parliament can have no confidence in the SNP ‘pick a figure out of thin air’ approach to budgeting.” 

Ms Slater responded: “We acknowledge the comments and recommendations made by the Finance Committee.

“We want to create a circular economy, in which resources are kept in use for as long as possible. This is not just good for the environment – it will also create new economic opportunities and green jobs here in Scotland.

“Our Circular Economy Bill will establish the legislative framework to support that. The Bill is also expected to bring benefits to local authorities, for example as a result of less contamination of recycling, and savings made through waste collection and disposal costs, including reduced litter costs.

“The financial memorandum provides strategic-level cost and benefit data which will be refined as part of ongoing work with local authorities and householders, businesses and other stakeholders.”