Lord Frost has been tasked with taking on the European Union over its "heavy-handed" approach to the Northern Ireland protocol, The Telegraph understands.
The Government regards the bloc's application of the agreement as "overly legalistic" and is hoping to agree a softer interpretation of the rules to ease problems facing UK traders crossing the Irish Sea, according to insiders.
Boris Johnson appointed Lord Frost, his Brexit negotiator and a key ally, to the Cabinet on Wednesday night in order to take the UK lead on relations with the EU in the post-Brexit era.
The Prime Minister switched out Michael Gove from the role as part of a move to adopt a tougher stance on Brussels over the protocol, according to Whitehall sources.
Ministers harbour concerns that the EU has failed to understand the seriousness of its aborted move to trigger Article 16 of the protocol last month, effectively creating a hard border for vaccine supplies between Northern Ireland and the Republic of Ireland.
The situation on the ground is still "fractious" and a fix that takes into account political sensitivities is needed to solve the issues traders are facing as a result of the Northern Ireland protocol, Government sources warned.
The current arrangements have heightened political tensions, with unionists and loyalists angered at the imposition of economic barriers between Northern Ireland and the rest of the UK.
Bureaucracy and checks required under the protocol, which was established to smooth trade friction due to the province remaining in the UK internal market while continuing to apply some EU rules, have hampered movement of some goods entering the region from Great Britain.
On Thursday Maros Sefcovic, the European Commission vice president, insisted he was committed to finding pragmatic solutions to the issues facing traders after Brexit.
He and Mr Gove, who remains a Cabinet Office minister until the handover to Lord Frost on March 1, held virtual discussions with business representatives affected by disruption associated with the Northern Ireland Protocol.
Mr Sefcovic said he enjoyed "constructive meetings with business and civic society in Northern Ireland on challenges they face on the ground".
Traders have called for pragmatism and political will on the part of the EU, which is part of a Joint Committee with the UK overseeing the protocol's workings.
Arlene Foster, the Democratic Unionist Party leader and First Minister of Northern Ireland, welcomed Lord Frost's appointment and said she hoped it hailed the UK taking a more hardline approach.
She told The Telegraph: "He needs to set his sights on a long-term solution rather than sticking plasters. Whether it is the flow of parcels, supermarket goods, chilled meats or medicines, from GB to NI, the United Kingdom single market has been ruptured."
The DUP, which believes the protocol is inherently flawed and should be scrapped, has been increasingly critical in private of Mr Gove's approach, which has been aimed at resolving problems experienced by businesses within the protocol.
It is not thought that Lord Frost will try and renegotiate the protocol, but he is expected to examine all avenues to soften problematic aspects of its implementation.
A number of grace periods, which limit the certifications and declarations required to move goods, are due to lapse in coming weeks and months. Exemptions related to checks on some supermarket goods and customs declarations on parcels are due to end at the end of next month.
Mr Gove has urged the Commission to grant extensions until January 2023 in order to provide space to find resolutions.
Mrs Foster countered that extensions to grace periods were temporary measures and "do not provide the certainty Northern Ireland deserves".
Following the virtual meetings between Mr Sefcovic and Mr Gove on Wednesday, Northern Ireland Retail Consortium director Aodhan Connolly said it is vital the views of businesses were heard.
"This was an important meeting but it must be the start of a comprehensive dialogue including the establishment of a business consultative body to ensure the EU and UK can hear business concerns and use the expertise of the NI business community in finding solutions to the challenges we face," he said.
He warned that the looming April 1 deadline for the end of a number of grace periods could heap "unprecedented pressure" on supply chains. Traders and retailers need stability, certainty, simplicity and affordability, he said.