A bus carrying demonstrators drives past the Supreme Court in London, Britain on Dec. 5, 2016. The British Supreme Court on Monday morning started hearing the historic Brexit legal case to decide whether the British government can begin the process to pull Britain out of the European Union (EU) without a parliament approval. (Xinhua/Tim Ireland)

LONDON, Jan. 3 (Xinhua) -- Britain's ambassador to the European Union (EU), Sir Ivan Rogers, has quit his job in Brussels, according to a report in the Financial Times (FT) on Tuesday.

A spokesman with the British government also said in a brief statement that "Sir Ivan Rogers has resigned a few months early as UK Permanent Representative to the European Union.

The sudden decision came just weeks after Rogers was accused of damaging the Britain's Brexit negotiations.

Rogers had warned that it would take a decade to forge a new trade deal with Europe, saying that was the view of the other 27 member states with the bloc.

Political commentators said the relationship between Rogers and the government had become strained over the grim warning of a prolonged Brexit.

Rogers was appointed to the role of permanent representative in 2013 by former prime minister David Cameron.

He had been expected to play a key role in Brexit talks expected to start within months after Cameron's successor at 10 Downing Street, Theresa May, triggers the exiting process in March.

Rogers was due to quit his job in Brussels towards the end of this year, but has decided to go earlier "after tensions with Downing Street," according to the FT report.

Rogers' quit triggered mixed reactions in political circles with some expressing dismay and others delighted.

The Daily Telegraph said news of the resignation prompted concerns that Britain would get a worse Brexit deal than it would have done if he was part of the team.

At the think-tank, the Center for European Reform, director Charles Grant, said "Ivan Rogers' resignation makes a good deal on Brexit less likely. One of the very few people at top of British government who understands EU."

But the campaign group Leave.EU was delighted over Rogers' leave.

The pro-Brexit campaign group said on its website: "Pessimist Rogers, who warned Brexit would take 10 years, is to leave his post as UK Ambassador to the EU. Good - time for some optimism!"

Meanwhile, some, including the Labour MP Hilary Benn, who chairs the Brexit select committee in the House of Commons, are urging for a quick appointment of a new ambassador to replace Rogers.

"It couldn't be a more difficult time to organise a handover," Benn told local media in London.

Oxford-educated Rogers, as Britain's Permanent Representative to the EU, has overall responsibility for the work of the mission and represents the British government at weekly meetings of the Committee of Permanent Representatives in the Council of the European Union.

The committee deals largely with political, financial, justice, policing and foreign policy issues.

So far the Foreign and Commonwealth Office in London has not commented on the resignation.