The sale of glue traps to control rats and mice in Scotland has become the latest constitutional battleground between the SNP/Green administration and the UK Government.

A ban on the sale of glue traps were part of the Wildlife Management and Muirburn Bill passed by MSPs in March.

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However, the move fell foul of the Internal Market Act (IMA) – designed to limit trade friction across the UK – forcing Scottish Government ministers to seek an exemption from the act, although rural affairs remain largely devolved to Holyrood.

Recently appointed Scottish Agriculture Minister Jim Fairlie wrote to Defra, but the request was snubbed by Lord Douglas-Miller.

The Scottish Government quotes the response from Douglas-Miller, arguing the ‘UK Government does not consider that the evidence presented demonstrates that a ban on the sale of glue traps would be substantially more effective than a ban focused on their use and possession’.

It adds: “The UK Government therefore does not believe that the case has been made that an exclusion under the UKIM Act is necessary to deliver the policy aims of restricting the use of these traps in Scotland.”

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The refusal triggered an escalated response from Deputy First Minister Shona Robison. In a letter to Steve Barclay, the food and rural affairs secretary, Ms Robison slammed aspects of the refusal as ‘simply illogical’.

She added: “Is it really the UK Government’s position that a product already subject to a ban on its use and possession cannot also be banned from sale due to the need to avoid barriers to trade wherever possible?

“However, the issues run deeper: the letter also suggests that the UK Government believes it is legitimate to use the IMA – ostensibly a legal regime to protect intra-UK trade – to effectively overturn a policy approved by the Scottish Parliament.”

Ms Robison continued to slam the decision, adding: “It is not credible to claim that this decision is intended to avoid trade barriers and unnecessary disruption of economic and trade flows, given that in this case, the trade and economic impact is negligible to non-existent.

“This decision underlines once again the flawed nature of the IMA, where the complete absence of any proportionality principle – an essential feature of any well-functioning internal market system – lays bare the glaring inconsistency between the Act’s stated purpose and its operation in practice.”

The exchange of letters has been criticised by Scottish Conservative rural affairs spokesperson Rachael Hamilton. She said: “This is the latest typical of example of the SNP’s constitutional grievance. They are trying to paint this as a row about animal welfare, when the reality is that they are just using this to stoke a row with the UK Government.

“Ministers should know fine well that this was not going to meet the threshold for an exemption within the IMA.

“They should be focusing more on why they brought their own amendments on the subject forward so late, that there simply was not the time for MSPs to scrutinise them.

“SNP ministers should be looking to work closely with the other parts of the UK and recognising the circumstances in which glue traps would still have to be used, and often on a cross-border basis.”

A spokesman for the UK Government said: “We are pleased that the Scottish Government is also pursuing a ban on the use of rodent glue traps, but do not believe the evidence presented has demonstrated that a new trade barrier is necessary when it appears a ban on their sale would not be substantially more effective than one focused on their use and possession.”

The use of glue traps is already banned in England and Wales, but their sale is not.