"So government wants to prolong it but business wants certainty (but) there is a dichotomy between what business wants and what government can do. I think the negotiations are going to be very tough."
Sorrell's comments come after Theresa May, the former U.K. home secretary, was appointed as U.K. prime minister on Wednesday. Shortly after meeting the Queen as part of the formal process of becoming leader, May returned to her new residence of 10 Downing Street and announced her cabinet with a mixture of pro-EU and Brexit campaigners appointed to the top jobs.
Former Foreign Secretary Philip Hammond replaced George Osborne as finance minister (Hammond campaigned for Britain to stay in the EU) and Boris Johnson, the outlandish former London mayor and prominent Brexit campaigner became foreign secretary – raising eyebrows in Westminster and some laughs on social media site Twitter.
Amber Rudd is the new home secretary and Michael Fallon is the new defense secretary; both were remain campaigners. Leave campaigner and long-time Euroskeptic David Davis was appointed "Secretary of State for Exiting the EU."
The Bank of England's Monetary Policy Committee could cut interest rates by 25 basis points to 0.25 percent on Thursday in order to prevent the U.K economy from deteriorating in the aftermath of the vote.
Large companies like WPP, which employs over 194,000 people around the world, are in wait-and-see mode as a question mark remains over when the U.K. will actually start the withdrawal process from the EU, a process that could take two years or more given the complexity of the relationship.
Sorrell noted that while the share price of his own company had been resilient in the wake of the vote and that sterling had strengthened following more political certainty, the Brexit vote "has had a serious impact on the U.K. economy."
"All the data that we've got over the last two weeks indicates that consumer confidence and corporate confidence was battered by what happened, certainly in the short-term. Businesses are looking for excuses not to do things and the key thing is to restore long-term confidence," he said.
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