EDINBURGH/LONDON (Reuters) - Lawmakers from the Scottish National Party (SNP) walked out of the British parliament on Wednesday to protest what they say is Scotland’s voice being ignored over Brexit.

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The SNP’s Ian Blackford was thrown out of the chamber by the speaker of parliament because he refused to sit down after demanding a new debate on Scotland and Brexit. Opponents said the move was planned well in advance, taking place during prime minister’s questions, the highlight of the parliamentary week.

Blackford was followed by the rest of the SNP’s 35 lawmakers. He told the BBC later that the government was rolling over Scotland to get legislation intended to provide Britain a legal framework once it leaves the European Union.

“Let’s be under no illusion - this is a constitutional crisis,” he said.

The SNP says it will now seek to build a new power-sharing deal for Scotland, Brexit minister Michael Russell told Reuters. Such a complex endeavour is bound to complicate the agenda of Prime Minister Theresa May as she tries to negotiate Brexit.

Differences over Brexit have strained relations between the United Kingdom’s four nations. Scotland and Northern Ireland voted to stay in the EU in a 2016 referendum, while Wales and England vote to leave.

On Tuesday, British lawmakers voted to push through Brexit legislation that included measures affecting Scotland such as agriculture and fisheries. But Scotland’s devolved parliament, Holyrood, had rejected those measures last month with the backing of all parties save the Scottish Conservatives.

May told parliament that most areas of responsibility that Holyrood has now will continue after Brexit, and accused the SNP of stoking grievance.

Most Scottish lawmakers are unhappy at a clause in the EU withdrawal bill that temporarily restricts the Scottish, Northern Irish and Welsh assembly’s powers, leaving them in the hands of the UK government while the rules governing Britain after Brexit are redrawn.

Scots are unhappy that it is unclear when those powers - over agriculture, fisheries and food labelling - will be given back, potentially tying Holyrood’s hands for years. The SNP calls it a “power grab,” something the UK government denies.

“I’m in favour of independence, but while devolution continues to exist it can’t operate like this. This is essentially destroying it, refusing to accept the rights of the parliament and refusing to accept its view,” Michael Russell told Reuters in a telephone interview.