Safeguarding The Union deal: Former DUP deputy leader Lord Dodds warns 'the fundamentals' of Windsor Framework remain in place despite deal by his leader Sir Jeffrey Donaldson

Lord Dodds of Duncairn said many unionists were also worried about the continued application of EU law in Northern Ireland, signalling tensions within the party over the Government’s efforts to revive Stormont.

The House of Lords heard from the DUP peer as the Commons approved fast-tracked legislation aimed at addressing concerns about post-Brexit trade arrangements in Northern Ireland which have led to a two-year DUP boycott of devolved government.

The DUP’s leader, Sir Jeffrey Donaldson, has said the changes he agreed to would restore Northern Ireland’s place in the UK single market.

But Lord Dodds suggested there was a divergence of views within the party, telling peers: “Will he accept, and your lordships in this House need to realise, that there are still many unionists who are deeply worried and concerned that the Irish Sea border… still exists, since many goods coming from Great Britain, British goods coming to Northern Ireland, especially in manufacturing, still need to go through full EU compliance checks, procedures.

“Whilst we have the new green lane which is mainly for retail, the default position is as I’ve described for everything else that doesn’t have an end point for sale in Northern Ireland.

“Will he also confirm the concern that there is among many unionists – and he knows Northern Ireland very well – at the continued sovereignty, jurisdiction and application of EU laws over large swathes of our economy in 300 areas, to which the Stormont brake doesn’t apply and we cannot make or amend laws within those areas.

“These are fundamentally important constitutional and economic issues and many unionists still are concerned about these issues.”

Lord Dodds also argued that “the fundamentals” of the Windsor Framework remained in place despite the planned changes.

Northern Ireland Office minister Lord Caine said the Government did not recognise there was “anything like a trade border” in the Irish Sea.

He said: “I am sorry to say to him that the Government does take a very different view as a result of the deal that has been agreed over the past few days, as indeed I should gently point out does his party leader, who along with the Government now accepts that what we have agreed is a firm basis for going back into the institutions and re-establishing the executive and the Assembly at Stormont.

“We simply don’t recognise that what he describes is anything like a trade border between Great Britain and Northern Ireland. As a result of this deal the number of goods that will pass through into Northern Ireland without checks will be significantly increased.”

The minister also faced calls from senior Labour figures to reform the way in which Northern Ireland’s devolved government is formed to prevent powersharing from collapsing in future.

Speaking from the frontbench, Labour former Northern Ireland secretary Lord Murphy of Torfaen said “we don’t really want to see all this happening again”.

Fellow former Northern Ireland secretary Lord Reid of Cardowan said: “It is an unfortunate reality that the present construction lends it open to a number of parties, including the British Government, to suspend the Assembly.

“So I think it is wise for the minister to agree that the mechanics needs looked at again but even wiser to recognise that it has to be done with great caution and it has to be led by the parties in Northern Ireland themselves.”

Lord Caine replied: “We should be cautious in our approach to reform. Sensible, practical reforms ought to be considered where consistent with the agreement, but the conversation should primarily be led by the parties in the executive and the Assembly.

“The history of trying to impose reforms and solutions on Northern Ireland without the consent of the people is not necessarily a happy one.”