Pierre Moscovici
Pierre Moscovici warned the UK's decision to leave the European Union was a blow to both parties Reuters

Britain's decision to leave the European Union will be a damaging blow for both the UK and the soon-to-be 27-country bloc, according to Pierre Moscovici, the European Commissioner for Economic and Financial Affairs.

Speaking at the World Economic Forum in Davos, Switzerland, on Thursday (19 January), Moscovici said the UK would face weaker economic growth outside the bloc, adding the split would be damaging for both parties.

"You cannot have all the advantages of being a member of the club when you are out of the club," he said.

"I think that our British friends who invented clubs can understand that. We are and we must remain strong partners. To us you must understand that it is also a wound."

Earlier this week, Theresa May, who will address the World Economic Forum at 9.15am GMT today, set out her Brexit plan, indicating Britain will leave the single market but will pursue a "bold and ambitious" Free Trade Agreement with the European Union.

However, Moscovici cautioned Britain's aim to retain some access to the single market could be complicated by the Prime Minister's decision. "I am convinced that it is not an example to follow, that it's not positive neither for us neither for the UK," he said.

On Wednesday, Christine Lagarde, warned the UK's separation from the EU could be painful and complicated, adding it would not be all positive.

The managing director of the International Monetary Fund welcomed May's speech as it provided clarity. "Better clarity, less uncertainty is certainly better for the UK economy and for the rest of the European Union," she said.

However, she warned that there were still many questions that needed answers. "The terms under which the [agreement] will be facilitated, over what period of time – question mark.

"Over what kind of transition period – question mark. It is only when those questions are better clarified that we will understand how the UK economy is going to pan out. We are still of the view that it will not be positive all along and without pain."

Moscovici echoed Lagarde's words, stressing Britain and the EU would now have to agree a new strategy.

"Brexit means Brexit, which is to say that it is not the same to be out than in, and it cannot be better to be out than in, because it cannot be so," he said.

"We need to re-invent a new kind of relationship that I hope to be close, balanced and positive but that's the outcome of the negotiations not the starting point."