As debate began on the European Union (Withdrawal) Bill, both parties condemned it as a “power grab” that would strip Holyrood of its ability to legislate in some areas.
Downing Street has said it is in listening mode and will take on board MPs’ concerns about the bill, including on devolution, but that the bill was essential to delivering Brexit.
MPs have also warned the government that so-called ‘Henry VIII’ provisions in the bill gave ministers too much power to amend or scrap laws without consulting parliament.
The House of Commons will have eight days to make amendments at the committee stage following a vote on Monday, with pro-EU Tories threatening to back changes to curb ministerial powers.
Away from Westminster, the European Union warned the UK government’s plans for the Irish border after Brexit “will not happen” and suggested Brexit Secretary David Davis was not making himself “available” for negotiations in Brussels.
The Repeal Bill will transfer EU regulations into UK law, giving ministers a two-year window to amend or scrap individual provisions using secondary legislation, which cannot be amended and does not need to be debated by MPs.
It will also ring-fence powers currently held by the EU but exercised by devolved administrations, in areas such as agriculture, fisheries and the environment.
UK ministers insist many of these powers will be devolved soon after Brexit, but argue some need to be retained by Westminster to prevent differences in regulatory regimes that may produce internal trade barriers.
During debate, Mr Davis told MPs that some devolved responsibilities would have to be retained in order to “manage shared resources such as the sea, rivers and the air”.
“They will allow us to strike ambitious trade deals, administer and provide access to justice in cases with a cross-border element and enter into new international treaties,” he said.
But in a joint article, the shadow Brexit Secretary Sir Keir Starmer, the Welsh First Minister Carwyn Jones and shadow Scotland Secretary Lesley Laird said the devolution proposals in the bill were “completely unacceptable”.
Labour warned there were no limits in the bill to provisions that ring-fence EU responsibilities in devolved areas and claimed it would provide “a blank cheque for any future Tory Government to unilaterally claw back powers”.
And Labour also raised the heat over claims that Henry VIII powers give UK ministers greater licence to amend devolved law than Scottish ministers.
“A Tory Government is threatening to drive a coach and horses through that devolution settlement, using Brexit as a pretext for an unprecedented attempt to centralise power still further in Whitehall,” the three senior Labour figures said yesterday.
The SNP’s Europe spokesman Peter Grant claimed the government was “intent on not just taking back control from Brussels, but also from Scotland, Wales and Northern Ireland”.
Challenging Scottish Conservative backbenchers to rebel and vote against giving the bill a second reading, Mr Grant said: “Every elected Scottish MP will have a crucial role in either granting this Tory government a pass to simply do as it pleases, or stand with SNP MPs in the lobby and deny the power grab they seek to achieve.”