(Reuters) – Marks and Spencer Group Plc, a British retailer, told the UK government on Wednesday that European Union proposals regarding Northern Ireland’s post Brexit trade rules would lead to an increase in the administrative burden for imported goods.

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”.

Last month, the EU provided a range of measures that would ease goods transit from Britain to Northern Ireland. These included labelling in order to make sure British products don’t slip through the Northern Ireland backdoor to the EU single markets.

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 inspection suggests to us, that the proposals might end up being more expensive to implement EU customs controls,” the chair wrote in his letter. The chair called for a “risk-based” regime with restricted checks on goods and extensive use of digital tech, according to the FT.

M&S did not immediately respond to a Reuters request for comment on the same.

Frost indicated Wednesday that the government would prefer to make a deal for Northern Ireland to benefit from post-Brexit trading arrangements. He said that this agreement could be made by Christmas.