Arlene Foster, Northern Ireland’s first minister and leader of the Democratic Unionist party (DUP), has accused the EU of belligerence and inflexibility in its application of post-Brexit arrangements for the region. The EU commission was disrupting supply chains and damaging the Good Friday agreement through a “disproportionate” application of the Northern Ireland protocol, the part of the Brexit deal that keeps the region in the bloc’s single market, she said on Friday. “They have taken a very belligerent approach to the difficulties the protocol have caused for Northern Ireland,” Foster told BBC Radio 4’s Today programme. “The number of checks which are occurring between Great Britain and Northern Ireland are so disproportionate to the risk to the EU single market that it has become completely out of step with what the protocol was meant to do.” Her comments were the latest salvo in the DUP’s campaign to dilute or ditch the protocol, which requires checks on goods coming from Great Britain to Northern Ireland. They came amid an escalating row between the British government and Brussels, which said it would launch legal action following a move this week by the UK to unilaterally delay implementation of part of the protocol. The DUP and other unionist parties are angry with Boris Johnson for signing up to the protocol but they back his attempt to extend a series of “grace periods” to ease disruption of food supplies and parcel deliveries. “The protocol was meant to do two things. It was meant to protect the single market of the European Union, and it was meant to protect the Belfast agreement, and frankly it is disproportionately doing one, and damaging the other,” said Foster. The European parliament responded to Downing Street’s unilateral announcement by taking steps to delay formal ratification of the wider Brexit trade and cooperation agreement. The DUP’s Westminster leader, Sir Jeffrey Donaldson, said it showed the EU’s desire to punish the UK regardless of the impact on Northern Ireland. “Brussels is selfishly intent on using Northern Ireland as a bargaining chip. The UK government was wrong to agree the protocol and failed to see the impure motivations of the EU.” Tensions rose on Thursday when loyalist paramilitary groups withdrew support for the Good Friday agreement in protest at Northern Ireland’s Irish Sea trade border with the rest of the UK. The Loyalist Communities Council, an umbrella group that represents the views of the UVF, UDA and Red Hand Commando, demanded changes to the protocol but promised to stick to peaceful means. Simon Byrne, the chief constable of the Police Service of Northern Ireland, told the Policing Board the warning was a political move and that he did not think loyalists would return to violence. “We are prudently looking at an assessment of what that means in terms of a policing response or indeed any need to change our posture over the weeks ahead,” he said.