The Conservatives are trying to "unilaterally rewrite the devolution settlement", the Scottish Government has said.

Scotland's Brexit minister Michael Russell made the comments after a speech by UK Cabinet Office minister David Lidington, who is effectively Prime Minister Theresa May's deputy.

Lidington urged Scottish and Welsh ministers to come to an arrangement with May's government on the EU Withdrawal Bill.

He said Brexit must not be used as an excuse to break up the UK at "a crossroads in our history".

The UK and devolved administrations have been at odds for months on the so-called Brexit Bill, which would result in EU responsibilities in devolved areas being temporarily transferred to Westminster.

Both the Scottish and Welsh administrations have dubbed the legislation a "power grab" and say they will not recommend the devolved legislatures grant it consent in its current form.

Speaking at Airbus in North Wales on Monday, Lidington said the UK Government had made a "considerable offer" to the devolved administrations.

The offer, he said, included a commitment that the "vast majority" of powers returning from Brussels will start off at Holyrood, Cardiff Bay and Stormont rather than Westminster.

Lidington said: "Let's be in no doubt: this would mean a very big change to the EU Withdrawal Bill that is before Parliament and a significant step forward in these negotiations.

"This would put on the face of the Bill what we have always said was our intention: wide-ranging devolution not just away from Brussels, but from Westminster too.

"If accepted, this offer puts beyond doubt our commitment to a smooth and orderly departure from the European Union, in a way that doesn't just respect the devolution settlements, but strengthens and enhances them."

Under the plans, Westminster would only be involved where a "pause" was necessary to draw up a UK-wide framework to protect the "UK common market" or to meet international obligations, he said.

Lidington added: "Leaving the EU presents many challenges for our centuries-old union story - and opportunities too.

"Some want to use this as an excuse to loosen these ties that bind us together or even sever them completely.

"I believe such an outcome would leave every one of our four nations both weaker and poorer."

But Russell insisted the minister's proposals were merely an attempt to "dress up" the Bill.

He said: "However they try to dress this up, the reality is the UK Government is using Brexit to try to take control of devolved powers without the agreement of the Scottish Parliament.

"It is totally unacceptable for the Tories to unilaterally rewrite the devolution settlement that the people of Scotland voted for so overwhelmingly.

"We have always said we are not opposed to UK-wide arrangements on issues such as food labelling when they are in Scotland's interests - but the fundamental point of principle is that any changes to the powers of the Scottish Parliament, permanent or temporary, can only be made with the agreement of Holyrood.

"And it is only because Westminster wants to take control of devolved powers that there is any debate on this issue at all."

The minister added: "The UK Government's whole approach to Brexit to date makes a mockery of claims of a partnership of equals - they have failed to properly engage through the joint ministerial committee process, while no Scottish MP or minister was invited to the Chequers summit on the final shape of Brexit."

The First Minister of Wales, Carwyn Jones, also criticised the UK Government's "unacceptable" approach and described Lidington's comments as just "warm words".

He said: "I welcome the commitment of the UK Government to continue to work with us on their EU Withdrawal Bill.

"However, as currently drafted, the Bill allows the UK Government to take control of devolved policy areas, such as farming and fishing, once the UK has left the EU.

"This is an unacceptable attack on devolution in both Wales and Scotland.

"We now need further progress that goes beyond warm words and I hope the 'very big changes' promised in the speech equate to sensible amendments to the Bill which respect devolution."