Nov 17 (Reuters) - British retailer Marks and Spencer Group Plc (MKS.L) told the UK government that European Union proposals on Northern Ireland"s post-Brexit trade rules would increase the administrative burden on imported goods, the Financial Times reported on Wednesday. In a letter to UK Brexit minister David Frost seen by the newspaper, M&S Chair Archie Norman said that the proposals from Brussels "could result in worsening friction and cost and a high level of ambiguity and scope for dispute". The EU offered a package of measures to ease the transit of goods from Britain to Northern Ireland last month, including labelling to ensure British products do not slip into the EU single market via a Northern Ireland back door. read more The labelling requirement would add 9 million pounds ($12.14 million) in extra costs annually for the 90 million products M&S ships to Northern Ireland from the mainland, Norman said, according to FT. Required checks would result in fresh goods taking 45 hours longer to get to stores than when the UK was an EU member, Norman said, adding that M&S might have to stop sending some product lines to Northern Ireland, according to the newspaper. "Detailed examination suggests to us that the proposals could end up being more costly to implement than full EU customs controls," the chair said in his letter, calling for a "risk-based regime" with limited checks on goods that would make extensive use of digital technology, FT reported. M&S did not immediately respond to a Reuters request for comment on the same. Frost said on Wednesday that his government"s preference is to strike a deal to improve post-Brexit trade arrangements for Northern Ireland and that the agreement can be reached by Christmas. read more ($1 = 0.7415 pounds)