Advertising giant WPP (Frankfurt: A1J2BZ - news) has warned of increasing uncertainty facing the UK over Brexit - even as it reported a surge in profits and revenues helped by the post-referendum fall in the pound.
The global group, led by Sir Martin Sorrell, saw pre-tax profits climb 27% to £1.89bn in 2016 - or 12% when stripping out the effects of the plunge in sterling.
But UK revenues fell in the final quarter of the year and WPP said weakness in the latter half of 2016 may have reflected "Brexit uncertainties".
The group also warned of "tepid economic growth" for 2017 and Sir Martin said tough competition as clients looked to cut costs meant the ad market environment was "very difficult". Shares (Berlin: DI6.BE - news) fell 8%.
WPP painted an optimistic picture of the impact on the US of Donald Trump's policies, as he plans to cut tax and invest in infrastructure, but was cautious about the UK as it faces life outside the EU.
"The prospects in the United Kingdom are more mixed as the post-Brexit vote scenarios will play out over the next two years and uncertainties about the possible outcomes increase," WPP said.
It follows a warning from the CBI on Thursday about the dangers of leaving the EU without a trade deal - opening a "Pandora (LSE: 0NQC.L - news) 's Box (Frankfurt: 3BX.F - news) " of unforeseen consequences, such as export tariffs of 90%.
There were warmer words from WPP about the Trump administration's pro-business stance after Sir Martin's previous criticism of the President's controversial travel ban.
The company said prospects in the short to medium term were "strengthening under the Trump administration".
WPP said the Trump White House was "much more strongly pro-business, much more business-connected than the Obama administration".
It pointed to plans for "pro-growth tax, infrastructure investment, spending and regulatory reform".
UK-based multinational firms benefit from weakness in the pound because it means income from overseas is worth more when brought home.
Steve Clayton, fund manager at Hargreaves Lansdown (Frankfurt: DMB.F - news) , said: "WPP delivered profits ahead of market expectations for 2016, but is sounding a note of caution for the year ahead."