The first ministers of Wales and Scotland are joining forces to oppose Boris Johnson’s Brexit Bill.
Nicola Sturgeon and Mark Drakeford have accused the UK government of trying to rush through the EU Withdrawal Agreement without “detailed scrutiny”.
They are urging the prime minister to allow more time for the bill.
It comes after Boris Johnson “paused” his Brexit bill after the Commons rejected his plan to get it signed off in three days.
Ms Sturgeon and Mr Drakeford are due to hold a joint press conference at Westminster calling for the devolved nations to be given a greater say.
Ms Sturgeon will tell the conference: “The UK government has sought to pass the Withdrawal Bill through Westminster without an opportunity for detailed scrutiny in either the UK or Scottish Parliaments. That is unacceptable.
“It is imperative that this bill is subject to detailed scrutiny in all of the UK’s legislatures and that the views of the Scottish Parliament and Welsh Assembly are taken into account.”
The two first ministers have jointly written to Boris Johnson and the president of the European Council asking for an extension to give more time to scrutinise the bill.
They are expected to warn that Brexit will damage devolution and be disastrous for the economies of both Scotland and Wales.
Mr Drakeford will say: “The first minister of Scotland and I have jointly written to the prime minister and the president of the European Council asking for an extension so that the Scottish Parliament and the Senedd can fulfil their constitutional duty and properly scrutinise the Withdrawal Agreement Bill.
“There is another way – a referendum which gives people the chance to accept Johnson’s deal or choose to remain in the EU. We think remain is the right answer for Wales.”
The prime minister told MPs on Tuesday he would “pause” the Withdrawal Agreement Bill until the EU took a decision on whether to grant another extension to the current Brexit deadline of 31 October.
Mr Johnson said: “I will speak to EU member states about their intentions. Until they have reached a decision we will pause this legislation.”
He added: “Let me be clear. Our policy remains that we should not delay, that we should leave the EU on 31 October and that is what I will say to the EU and I will report back to the House.
“And one way or another we will leave the EU with this deal, to which this House has just given its assent.”