An SNP backbencher has accused Lorna Slater of having “no clue” after she insisted she has “ten out of ten” confidence in the finances of key environmental legislation despite admitting the final costs and timescales are not known.

Ms Slater, the Green Circular Economy Minister, came under intense pressure in front of Holyrood’s Finance Committee over a financial memorandum (FM) for her Circular Economy Bill.

Part of the legislation sets out a framework for future laws that could restrict or ban certain single-use products.

The financial memorandum states that the costs to the Scottish Government for the legislation are estimated at £1.5 million over the first three years of implementation, while it is expected to cost local councils around £227,000 each for the first three years.

It is estimated that local authorities could make savings of between £430,000 and £991,000 in the second and third years.

The costs for the Scottish Environmental Protection Agency (Sepa) is estimated to reach £888,000 over the first three years.

But costs to individuals or businesses have not been set out due to “the number of variables”.

But Ms Slater told MSPs that she remains completely confident that the estimated costs will remain as they are, despite not knowing what future secondary legislation for specific parts of the strategy will entail.

That boast of confidence came after council leaders told the committee that their confidence is around four or five out of 10, due to the lack of detail.

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Asked what she would give her confidence in the finances out of ten, Ms Slater told MSPs it was “ten in this FM because it is a strategic one”.

SNP MSP Michelle Thomson asked Ms Slater to clarify that “the costs given in this FM will be the final costs to the Scottish Government and to taxpayers of implementing this”.

Ms Slater said she agreed “because it’s at a strategic level”.

She added: “Within the FM, the assumptions that are made are very clear, as well as the ranges we are looking at.

“Most of the provisions in this bill are about setting up the frameworks, developing processes, developing legislation.

“The costs there are as indicative and as accurate as we can possibly make them for those things.”

But Ms Thomson, seen as an SNP critic of the Greens, warned that “this concerns me greatly”, adding that local authorities “don’t know the final costs”.

She said: “Imagine if you were going to build your own house and you went to the bank and said ‘I think I want to borrow £250,000 but it actually might be £1.75 million and I’ll let you know once I’ve been through all the various stages’.

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“They would be looking for considerably more detail.”

Ms Thomson added: “So why, given that tightness where we’ve got critical fiscal constraints, do you think it’s acceptable for us as a finance committee to sign off an FM where frankly we have no clue?

The Herald: SNP MSP Michelle ThomsonSNP MSP Michelle Thomson (Image: PA)

“We have no clue and I personally find it extremely difficult to have the right level of confidence because there’s so many variants.”

Ms Thomson labels the degree of variants “unbelievable”.

Conservative MSP Liz Smith, further grilled Ms Slater over his assertion that she has ten out of ten confidence in the finances of the legislation.

Ms Smith warned that “there is a big question about the ongoing co-design of the policies”.

She added: “It is very clear from the evidence we have taken so far that local authorities are not at all confident that the extent of the co-design is either certain or in terms of the timescales, is very clear.

“Why do you have ten out of ten confidence in this financial memorandum?”

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The minister stressed “that process is going to take some time in working with local authorities”.

She added: “This is all set out in good faith that we are providing the best information we can that we have at this moment.

“I am confident that we are providing you with the best information that we’ve got at this time.”

But the Tory MSP stressed that “just to put it out in good faith isn’t enough”.

She added: “If that co-design process is extended, almost indefinitely as far as I can see in this case, then it is almost impossible for us to scrutinise the final numbers of a financial memorandum.

“Because that detail is not there, our job is pretty well impossible.”

Ms Slater told the committee “that detail will be presented through that secondary legislation and will undergo all that parliamentary scrutiny”.