DOUGLAS Ross has been urged to show he is really a “defender of devolution” by voting for “devolution-protecting” changes to a controversial Westminster trade bill.

The Scottish Conservative and his five MP colleagues have been challenged by stalwart Liberal Democrat peer Lord Ming Campbell to show their support for devolution in the voting lobbies as the UK Internal Market (UKIM) Bill returns to the House of Commons tomorrow.

The Bill has caused problems for the UK Government since June, when Northern Ireland Secretary Brandon Lewis told MPs that it would break international law if it passed, as it would undermine the agreement the UK made with the EU over Northern Ireland.

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However, the Scottish and Welsh Governments have also argued the Bill, which is intended to set a plan out for trade among the four nations of the UK when the Brexit transition period ends, is an attempt to snatch power from devolved governments.

Having travelled through the House of Lords, several amendments have been made to the legislation which are focused on devolved governments having more input into decisions made by Westminster on trade and standards.

These are to be voted on tomorrow by MPs in what is described as parliamentary "ping pong".

It is expected that the Conservatives will not vote for the amendments, which include removal of the section which would break international law, and ensure consent was sought from devolved governments on certain regulations.

The Lords also agreed that there should be someone from Holyrood, Stormont and the Senedd on the Competition and Markets Authority.

In addition, they proposed to retain the previously agreed methods for deciding how to implement regulations that were controlled by the EU once those regulations return to UK control.

Lord Campbell said Ross must vote in support of the amendments to prove he truly believes in supporting devolution.

He said: “The question for the Scottish Tories, whose leader in Holyrood [Ruth Davidson] is an unqualified supporter of devolution, is whether the Scottish MPs are going to do the right thing and vote for the amendments which serve to support, and enhance, the devolution settlement.”

The former Liberal Democrat leader said it was vital the Scottish Conservatives support the changes to the UKIM Bill, following the remarks by the Prime Minister last month that devolution had been a “disaster”, and Tony Blair’s “biggest mistake”.

Leader of the House Jacob Rees-Mogg also said Labour under Tony Blair had taken a “wrecking ball” to the constitution, which had “weakened our Parliament and has helped to divide the United Kingdom”.

Lord Campbell added: “The House of Lords has done its very best to ensure that the devolution settlement is not impaired here.

"These comments from the Prime Minister Boris Johnson and from the Leader of the House are entirely consistent with the fact that the Tories to begin with did not join the constitutional convention which eventually gave birth to the Scottish Parliament, and campaigned vigorously against the Scotland Act in1988.

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"It is time the Conservative party stepped into the 21st century and do what is necessary for the preservation of the union.”

A Scottish Conservatives spokesman said: “The Internal Market Bill is essential legislation to protect trade across the UK, which supports half-a-million Scottish jobs, after we leave the EU.

“The Liberal Democrats have always opposed Brexit, so it’s entirely expected that they would try to delay and block any legislation related to it.

“The Scottish Conservatives have a proud record of strengthening Scottish devolution, including through the 2012 and 2016 Scotland Acts, and welcome that leaving the EU will result in more powers for the Scottish Parliament.”