Michel Barnier, the EU's chief Brexit negotiator, is to become a special adviser to European Commission President Ursula von der Leyen on the treaties ruling Britain's life outside the bloc. "I am pleased to share that Michel Barnier has been appointed special adviser to the president," commission Vice President Margaritis Schinas said. "He will advise our president on the implementation of the withdrawal agreement, as well as on the ratification process and the trade and co-operation agreement." In a tweet, Mr Barnier said he was honoured to continue working with the commission "for a few weeks". He said he would continue working with EU member states and the European parliament "to ensure smooth ratification on the EU side" of the Brexit withdrawal treaty and associated agreements. Mr Schinas said European Commission Vice President Maros Sefcovic would be the EU representative on a joint partnership council to be set up with Britain, which will guide interpretation of the trade agreement. Mr Sefcovic chairs the joint committee overseeing implementation of the withdrawal agreement. The commission said that its task force for relations with the UK, led by Mr Barnier, would cease to exist on March 1 and would be replaced by "a new service for the EU-UK agreements". It will be part of Ms von der Leyen's secretariat general. Mr Barnier, who reached the Commission's mandatory retirement age of 70 on January 9, will become special adviser from next month, Mr Schinas said. Issues likely to be priorities for him will be trade friction between Northern Ireland and the rest of the UK, which has have left some supermarket shelves bare, and the EU's ratification of the trade agreement. Britain's Parliament has already enshrined the deal into UK law but the EU is implementing it pending ratification by the European Parliament. The agreement stipulates that EU ratification must happen by February 28, but the joint partnership council could agree to delay that if more time were needed.