DEVOLUTION deals in the UK must be rewritten to stop Brexit battering farming, fishing and the environment, a think-tank claims.

Constitutional experts at the London-based Institute for Government (IfG) insist Westminster must reach new agreements with leaderships in Holyrood, Cardiff and Belfast.

The intervention is the latest in the argument surrounding the repatriation of key powers from Brussels.

Last month the Scottish Government’s Continuity Bill passed its second stage as ministers aim to protect the parliament from what it calls a “power grab” on the part of the UK Government.

The legislation aims to ensure legal continuity if the governments cannot reach agreement over the UK Withdrawal Bill.

However, British ministers claim they must take control of powers on fishing, farming and other issues that affect devolved areas of responsibility to harmonise systems and make business easier.

Months of negotiations have failed to produce a consensus and the IfG says the issues shows the “strain” on the constitutional settlement.

Jill Rutter, IfG Brexit programme director, said: “The past year has shown the strain leaving the EU is placing on devolution arrangements designed on the assumption of UK membership.

“It is time for an overhaul. It is in the interests not only of the UK government, but also the devolved governments, to develop firm foundations for future joint working – to promote collaboration and innovation.

“Only then will we have the right environment, agriculture and fisheries policies for the whole country after Brexit.”

Wrangles over cash for farmers will be one of the biggest challenges ministers face, according to an IfG report released today.

The UK received £3.4 billion in Common Agricultural Policy (CAP) payments in 2016, with England allocated less per head than other nations.

According to the body, the share was £177.64 per person in Northern Ireland, around £94 in Wales and Scotland and £41.46 in England.

As well as an agreement on how money should be allocated after Brexit, a decision must also be taken on what restrictions are placed on how the funding is spent, the IfG said.

Although some of it will fall under international rules, such as World Trade Organisation (WTO) regulations, they will not be enough to prevent market distortion within the UK.

In an example, the report states: “Current WTO rules would not prevent the Scottish Government from substantially subsidising beef farmers, even if the UK Government chose not to do so in England, which would give an advantage to Scottish beef farmers trading within the UK.”

The IfG called for an urgent review of the Joint Ministerial Committee and agreement on new ways of dealing with international trade and processes for settling disputes, according to the report.

It further recommends that Westminster parliamentary committees hold joint probes with Scotland, Wales and Northern Ireland in relevant areas and says the creation of public bodies to replace EU institutions should be “four-nation by default”, including Environment Secretary Michael Gove’s plan for an environmental watchdog for England.

The UK Government said: “We have undertaken a great deal of work to strengthen our relationships with the devolved governments as we prepare to leave the EU.

“We want to ensure the Joint Ministerial Committee is as effective as possible for all members and have implemented several changes to improve its function.

“The government recognises the need to review the existing intergovernmental structures and that is why at the most recent Joint Ministerial Committee the Prime Minister put forward a proposal to do just that.

“The UK government will work in collaboration with the devolved administrations to review our structures and make sure they are fit for purpose in light of our exit from the EU.”

The Scottish Government told The National: “Our position is clear – the devolution settlement must be respected. The people of Scotland voted in favour of devolution and against Brexit.

“We do note that the Institute’s report endorses our view that any new UK frameworks must be the result of agreement between the four UK administrations – they must not and cannot be imposed.”