Container ships are berthed on Jan 2 in Belfast, Northern Ireland, where concerns over border controls are rising. PHIL NOBLE/REUTERS Prime minister argues measures nation has taken are 'temporary' and 'sensible' The strained relationship between the European Union and the United Kingdom, a former member, took a turn for the worse this week with the bloc threatening legal action over alleged breaches of the Brexit deal that was agreed last year. The bloc believes the UK is breaking the agreement in Northern Ireland, which is part of the UK and therefore no longer within the EU but which shares a land border with the Republic of Ireland that all sides want to remain soft. The Brexit deal includes a provision called the Northern Ireland protocol that ensures goods can fl ow freely in and out of Northern Ireland, from both the EU and the UK, without border infrastructure in place. But London has struggled to implement the arrangements, which include customs checks far from the border, and goods have not fl owed as smoothly as planned, leading London to relax some rules. The Financial Times said the threatened legal action could end with the UK being clobbered with tariffs on imports. Maros Sefcovic, the EU's Brexit commissioner, wrote to his UK counterpart, David Frost, on Monday to explain that the bloc had made the move because the UK was "on a path of a deliberate breach of its international law obligations and the duty of good faith". He said, as the European Commission kicked off the process that could end in the UK being tried by the European Court of Justice, that the problem stemmed from the UK making decisions unilaterally. A spokesperson for UK Prime Minister Boris Johnson said London remained committed to the Northern Ireland protocol and any problems should be addressed by a joint committee established by the UK and the EU. Lengthy delays Britain's Daily Telegraph newspaper said Johnson's decision to unilaterally extend post-Brexit grace periods in Northern Ireland and to relax rules around checks on supermarket goods and parcels crossing the Irish Sea was in response to lengthy delays in getting items to Northern Ireland. The paper said the UK contends its actions are temporary and lawful and aimed at preventing disruption. The paper quoted Johnson as saying: "That's all we're trying to sort out with some temporary and technical measures which we think are very sensible." The Guardian newspaper noted that the threat of legal action was the second in six months, with proceedings launched last year in response to the UK planning to override the withdrawal agreement through its internal market bill. The paper said sources within the EU had explained that the bloc hopes the threat of legal action will register "discontent" but not lead to intervention by the courts. The sources said the bloc hopes to resolve the matter through negotiations, not the courts.