Powersharing in Northern Ireland could be threatened if unionists continue to agitate for the “unrealistic” scrapping of new Irish Sea trading arrangements, the SDLP has warned.

Colum Eastwood’s warning came as the Irish Government said it would be open to “modest extensions” of current grace periods that limit the bureaucracy associated with the contentious Northern Ireland Protocol.

Mr Eastwood urged the DUP to end talk of political boycotts and dial down the rhetoric, and instead join with other Stormont parties to find workable solutions to issues linked to the new regulatory and customs processes on Irish Sea shipments.

Calls from the DUP and other unionist parties in the region to ditch or suspend the protocol have intensified in recent weeks amid evidence of some disruption to trade arriving in the region from Great Britain.

Unionists and loyalists believe Northern Ireland’s position within the UK has been undermined by the protocol, which was incorporated into the Withdrawal Agreement to ensure a free-flowing Irish land border post-Brexit.

The DUP, which is urging the UK Government to bin the protocol, is pursuing a series of political moves aimed at undermining the mechanism, including a boycott on engagement with the Irish Government on issues related to its operation and a vow to oppose any protocol-related legislation at the Assembly.

The party also launched an online parliamentary petition aimed at securing a Westminster debate on the matter.

Asked by RTE if there could be a threat to powersharing if unionists took an increasingly hard-line approach to the protocol, Mr Eastwood said: “Yes, I think there could be and unionism needs to learn the lesson that they should have learned a number of times over the past 100 years – the British Government will let you down and if you keep going to the right you’re going to end up in a worse position when you come back to the table.

“So come and work with us, let’s get together, the spirit of powersharing is what’s important right now, working in partnership to deal with the problems.

“But continuing to run to the microphone, have petitions and talk about protests and all that – none of that works, it’s not based in reality.

“We know the DUP campaigned for Brexit, it was a strategic error at the time.

“We can now work together to resolve some of the difficulty, but let’s all calm down, work together, put the rhetoric at the door because it’s not going to help and it will have a political impact.

“We’re seeing stability being rocked this week in a number of different ways and I think as political leaders we all have a responsibility, first and foremost, to be honest with our people and tell them what the scenario is, what the context is, why we have trading barriers and also come together to work through it, because the alternative is just not worth contemplating.”

Inspections on animal-based produce arriving from Great Britain, which are required under the contentious Northern Ireland Protocol, were suspended at Belfast and Larne ports on Monday evening after menacing graffiti appeared.

Police blamed the graffiti and menacing online comments on disgruntled individuals and small groups, and have made clear there is no evidence of wider paramilitary involvement in threats.

Some workers returned to work on Friday but inspections have not yet fully resumed.

The UK Government and European Commission are due to hold further talks aimed at finding solutions in the coming week.

Cabinet Minister Michael Gove has suggested extending a series of grace periods that are currently in operation that limit the level of red tape associated with the protocol.

The UK Government wants to extend these exemption periods, some of which are due to expire at the end of March, to January 2023 in order to provide space to find permanent solutions.

Irish foreign affairs minister Simon Coveney said he would be open to limited extensions but he made clear there could be no renegotiation of the protocol’s terms.

“Certainly I would be open to advocating for modest extensions of grace periods when appropriate to try to, first of all, reassure people that we’re listening to them in Northern Ireland, because we are, and then, secondly, so that we can ensure that businesses can operate as best they can under the protocol,” he told RTE.

“But that’s not the same thing as scrapping the protocol and it’s important to make a strong distinction between the two.”

Ulster Unionist leader Steve Aiken said the UK Government needed to invoke Article 16 of the protocol to suspend its operation until issues causing disruption were addressed.

He said the protocol was “divisive, disproportionate and unfair”.

“Quite frankly, it’s bad law,” he told RTE.

“We know regrettably what happens when you have bad treaties and what it means for the overall relationships across these islands as we go on.

“That’s why called right at the beginning for the triggering of Article 16, because we need to get to the point where we actually put a pause to this before the three quarters of the Northern Ireland economy that depends on that East West linkage gets irreparably damaged.”

Sinn Fein President Mary Lou McDonald said Brexiteers had to accept that new trading borders between Great Britain and the island of Ireland were a permanent consequence of the UK’s exit from the EU.

Mrs McDonald said the focus needed to be on resolving initial problems with new Irish Sea trading arrangements, not ditching the protocol.

“Brexit is for keeps, I mean this is a big game changer for all of us and it has to be managed in a way that is sensible, in a way that is fair,” she told Sky News.