The European Union's chief Brexit negotiator, Michel Barnier, has ruled himself out of the race to become the head of the European Commission next year, saying he needed to remain focused on Brexit talks with Britain.

Jean-Claude Juncker, the current president of the Commission, is due to step down next year after European Parliament elections set for May.

Mr Barnier is from the centre-right European People's Party, the largest in the current European Parliament and had been mentioned as a possible successor to Mr Juncker.

"I have decided today not to run for the nomination as the EPP's European elections lead campaigner," Mr Barnier said in a letter to the party.

"We are in the final stretch of a serious and complex negotiation on the orderly withdrawal of the United Kingdom. It is my duty to remain engaged with all my energy and determination," he said.

Over the year-and-a-half of Brexit negotiations, Mr Barnier has greatly increased his profile by travelling extensively around the EU and holding meetings that have also included less-prominent regional leaders, labour unions and business.

The Commission has the initiative to draft EU laws, monitors compliance and acts as a competition watchdog.

A new executive will take over in November 2019.

The EPP is due to meet in the Finnish capital in November to choose a so-called "spitzenkandidat" - from the German for "lead candidate" - to lead its campaign for the European elections in May next year.

The group's nominee is expected to be a front-runner for the top job at the European Commission, the most powerful post in Brussels.

The "spitzenkandidat" method of selecting a commission president is not enshrined in EU law and Mr Barnier's decision not to seek the EPP nomination does not definitely rule him out.

Britain is due to leave the European Union in March next year following the 2016 Brexit referendum, but first Mr Barnier and Theresa May's team will try to arrange the terms for an amicable departure.