The UK Government has been accused of a "deliberate and premeditated attack on devolution" after leaked documents appear to show it hid key parts of Brexit planning from the Welsh and Scottish governments.
The documents, published on political website Guido Fawkes, appear to show ministers being warned that plans for the UK to assume control of state aid "should not be shared publicly or with the devolved administrations at this stage."
The proposal over state aid was finally published in the UK internal Market Bill.
A Welsh Government spokesperson has described the Bill as a "direct attack on devolution" and said the leaked documents "further corrodes trust in the UK Government."
The spokesperson continues: “Over the last two years, we’ve put the interests of our country first by setting aside our political differences and working constructively with the UK Government and the other devolved administrations to make sure we’re all as well prepared as we can be for the fundamental change in our relations with the EU which is coming.
"We're now calling on the UK Government to do the same and are requesting an urgent meeting with them to press home this point.”
The leaked documents are reported to have been given to ministers in June and contain detailed plans which have now appeared in the UK Government's Internal Market Bill.
Following the revelation, Plaid Cymru's Parliamentary leader said the documents "lay bare the cynical manipulation tactics of a rogue Westminster Government scheming to keep Wales in the dark."
In a letter to the UK's Business Secretary Alok Sharma, Liz Saville-Roberts said it showed "beyond a shadow of a doubt" that the UK Government were actively seeking to conceal information from the devolved governments.
The letter reads, "Deliberately keeping Welsh Government in ignorance about issues which will not only affect devolved policy areas, but which could have a profound impact on the lives of the people of Wales, is an abdication of duty. It is in direct contradiction to the principle of trust which should characterise relations between and among governments on these isles."
What is the Internal Market Bill?
The Internal Market Bill was introduced with the aim of ensuring trade between the four nations of the UK can continue to operate smoothly when the Brexit transition period finishes at the end of this year. It is designed to replace the European Union rules and regulations which currently shape the relationships of trade and investment here in Britain
It has already been passed by the House of Commons, however it has proved controversial because it could be used to override parts of the Withdrawal Agreement signed by the UK And European Union last year.
The UK Government is facing legal action from Brussels and Rhondda MP Chris Bryant said the legislation represented a "surrender of a key British value" during a meeting of the Commons foreign affairs committee on Tuesday.
The Welsh Government previously described the Bill as "an attack on democracy" and said it takes away powers and responsibilities responsibilities which have been devolved for 20 years.
Ministers in London acknowledge that it gives them new power to act and spend in devolved areas such as road-building but say the new rules are needed to ensure a level playing field for businesses in all parts of the UK.
In response, the UK Government said it "frequently" engages with the devolved administrations contingency planning for the end of the transition period.
A spokesperson said, "With fewer than three months until the end of the transition period, we will continue to work constructively with the Welsh Government and other Devolved Administrations to ensure the whole of the United Kingdom is ready for the changes ahead."
The Scottish Parliament is expected to vote against the Internal Market Bill and the SNP have said the leaked documents show the UK Government "cannot be trusted."
Kirsten Oswald MP, the SNP's deputy leader in Westminster said: "These leaked documents prove the Tory government deliberately hid crucial information about its extreme Brexit plans – including the likelihood of food shortages – from the devolved nations, as well as details about the Tory power grab on the Scottish Parliament."