SNP ministers may be forced to scale back controversial plans to ban fishing in one tenth of Scottish waters amid suggestion the UK Government could refuse permission for the full rollout of the proposals.

The Scottish Government has held an initial consultation on plans to designate 10 per cent of Scottish inshore and outshore waters as highly protected marine areas (HPMA) in a bid to tackle the climate crisis and help restore marine habitats.

Under the plans, no human activity, including fishing, will be allowed to take place in the HPMAs.

But in order to implement the legislation in full, SNP ministers will require the permission of the UK Government.

Prime Minister Rishi Sunak has already warned against the scheme, describing the Scottish Government’s plans as a “poor-thought-out” idea.

Now a UK Government source has told The Herald that the controversy around the proposals and the 10% ambition without any sites being identified could mean that Tory ministers withhold approval.

The UK Government is bringing forward its own HPMA proposals and has identified three initial zones, while environmental campaigners have called on ministers to go further in rolling out the plans.

Read more: Analysis: There's something fishy about the row over HPMAs

A Defra source told The Herald that it was “unlikely” that the UK Government would approve the plans “given the way the SNP has gone about business with fishermen in Scotland”.

They added: “We are bringing forward sensible plans but the Scottish Government’s plans could be seen as over-ambitious with their 10 per cent target before knowing where these zones can or should be designated.

“They shouldn’t be so sure that they will reach that threshold given that the entire proposal does not sit within devolved competence.”

But another UK Government insider acknowledged that officials and ministers were “not anywhere near” a decision being made on whether to approve or essentially block the plans.

It is thought that the discussions between the UK and Scottish governments have so far largely been in general terms rather than any specifics.

The Scottish Government’s consultation on the plans acknowledges that Holyrood “does not have the necessary legal powers to designate and protect HPMAs.”

The document adds that “the intention is to deliver the necessary legislative and management framework for HPMAs in both Scottish inshore and offshore waters”.

For the inshore region, up to 12 nautical miles from the coast, devolved powers allow for the HPMAs to be implemented with legislation at Holyrood.

But the paper admits that for the Scottish offshore region beyond 12 nautical miles out to the outer limits of the UK continental shelf, “powers over the marine environment are currently reserved to the UK Government”.

Read more: SNP minister says fishing ban 'will not be imposed' on communities

It adds: “We are seeking agreement from the UK Government to provide for equivalent powers for Scottish ministers to designate HPMAs in Scottish offshore waters.”

Scottish Liberal Democrat rural affairs spokesperson and Shetland MSP, Beatrice Wishart, said: “It’s hardly surprising that the Scottish Government could face serious challenges in taking this forward.

“So far, ministers have paid little to no regard as to how their rigid plans would impact costal and island communities. They failed to consult with communities before they brought the proposals forward- no wonder there is so much vehement opposition.

“Moving forward, the UK and Scottish Governments must work together with communities to find fair solutions. We need policies that are proportionate and evidence-based, protecting the biodiversity of our seas without threatening the futures and livelihoods of communities.”

Read more: SNP rebellion as McAllan defends fishing ban plans consultation

Scottish Conservative shadow rural affairs secretary, Rachael Hamilton, added: "The SNP-Green governments HPMA proposals are reckless and threaten to destroy many of our coastal communities.

"They have completely failed to engage with them and our fishing sector. It is time they urgently went back to the drawing board and scrapped their current plans."

A Scottish Government spokesperson said that “proposals for HPMAs are at an early stage”.

They added: “Scottish ministers have written to the Defra secretary of state to request powers to designate sites in Scottish offshore waters, on a similar basis to those previously granted for the designation of marine protected areas, and will continue to press for constructive engagement on this issue.

“The UK Government itself is in the process of designating three highly protected marine areas, including in offshore waters.

“We expect the UK Government to respect the will of the Scottish Parliament, as the policy around HPMAs progresses.”