NICOLA Sturgeon and Carwyn Jones have published a list of “substantial” demands they want to become law in order to protect their respective devolution settlements and prevent a constitutional crisis over Brexit.

In a joint letter to Theresa May, the Scottish and Welsh First Ministers said they stood ready to cooperate with the UK Government to prepare for the “upheaval of EU withdrawal”.

They said their amendments to the EU (Withdrawal) Bill would ensure devolved policy areas come back to the Scottish Parliament and National Assembly of Wales post-Brexit.

READ MORE: Scottish Government publishes list of 111 post-Brexit powers under threat from the UK

They added that the amendments would also prevent UK ministers unilaterally changing the Scotland Act and Government of Wales Act and would mean that agreement of the Scottish Government on necessary changes to current EU law in devolved areas after Brexit would be required.

The amendments would also ensure additional restrictions are not placed on devolved ministers compared with UK Government ministers, they said.

Publishing their demands, they described the EU (Withdrawal) Bill in its current format as a “power grab” that was “preventing this essential cooperation and coordination” and said they could not recommend giving consent to the legislation unless it is substantially changed.

In a joint letter to the Prime Minister, they said the Bill “can be made to work with, not against, devolution”.

First Secretary of State Damian Green said the UK Government would listen to suggestions to improve the legislation, but reflecting the stance he took last week suggesting powers over farming subsidies, for instance, would not be repatriated, he said ministers “will do nothing that risks undermining the benefits of the UK”.

“The UK Government stands ready to listen to those who offer improvements to the Bill – but we will do nothing that risks undermining the benefits of the UK,” he said.

“Cardiff, Edinburgh and Belfast will receive more decision-making powers as a result of this process.

But the UK Government will not risk our internal UK market, or make life more difficult or more expensive for UK companies, workers or consumers.”

The legislation, designed to transpose EU law into British law, will see EU responsibilities in devolved areas initially transferred to Westminster. The UK Government said this will allow common frameworks to be created ahead of further devolution. It has listed 111 and 64 policy areas returning from the EU which “intersect” with the devolution settlements of Scotland and Wales respectively.

The wide-ranging list includes agriculture, fisheries, the environment as well as, among others, food labelling, infectious diseases in animals and chemical regulations.

The First Ministers’ letter states that they want to work in “co-operation and in co-ordination with others to prepare for Brexit, but added: “We want a European Union (Withdrawal) Bill that can be made to work with, not against, devolution. The current Bill will need to be substantially amended for us to be able to recommend to our respective legislatures that they give their consent to it.”

The leaders said they have begun “to consider the scope for preparing alternative devolved legislation to provide for continuity of law on withdrawal from the EU” but have insisted that this is not their “preferred option”. Instead, they said their amendments, described as a “constructive contribution”, would enable progress to be made.

READ MORE: Scottish Government publishes list of 111 post-Brexit powers under threat from the UK

Scotland’s Brexit Minister Michael Russell said: “We have made it repeatedly clear we are not opposed in principle to UK-wide arrangements, but devolved policy areas must come back to the Scottish Parliament, where they properly lie, and then we can work towards an agreement.”

Labour joined the criticisms saying it was clear the Bill is “unsustainable” in its current form.

Deputy First Minister John Swinney and Russell meet Green in London on Monday.