A STRONG post-Brexit performance could give the UK economy a welcome fillip, according to a business organisation.

The International Monetary Fund (IMF) has lifted 2017 growth forecasts, saying a better-than-expected performance after the EU vote has raised prospects.

However, a simultaneous downgrade to the IMF’s forecast for 2018 points to a slowdown in Britain’s productivity.

The reports come as Prime Minister Theresa May prepares to set out her approach to Brexit negotiations in a speech today.

In its latest World Economic Outlook, the IMF said it now expects the UK economy to grow by 1.5 per cent this year, marking a 0.4 per cent upward revision to forecasts made in October.

The UK is among a number of countries - including the Germany, Japan and Spain - to see growth forecasts raised “mostly on account of a stronger-than-expected performance during the latter part of 2016,” according to the report.

It added: “Preliminary third quarter growth figures were somewhat stronger than previously forecast in some economies, such as Spain and the UK, where domestic demand held up better than expected in the aftermath of the Brexit vote.”

The UK’s Office for National Statistics said Britain’s economy expanded by 0.6 per cent between July and September last year.

However, the director of the IMF’s research department, Maurice Obstfeld, said Britain’s divorce from the EU was adding to uncertainty on the continent.

He added: “In Europe, Britain’s terms of exit from the EU remain unsettled and the upcoming national electoral calendar is crowded, with possibilities of adverse economic repercussions, in the short and longer terms.”

The IMF has downgraded its UK forecasts for 2018 by 0.3 per cent, with gross domestic product (GDP) growth for 2018 now expected to come in at 1.4 per cent.

It estimates Britain’s economy to have expanded by two per cent in 2016.

The figures could come under greater scrutiny today when Mrs May outlines the Government’s tactics in Brexit negotiations.

She is due to speak at London’s Lancaster House, where she is expected to outline her priorities on the UK’s withdrawal from the EU.

However, she has been accused by Labour leader Jeremy Corbyn of preparing to trigger a full-scale “trade war” with the EU, amid reports she is ready to pull out of the single market.