Optimism at major British companies has improved by the largest margin in at least 11 years after Prime Minister Boris Johnson won a sweeping election victory last month, according to a survey from accountants Deloitte.

Some 53% of chief financial officers at large businesses said their optimism about the financial outlook had improved compared with three months ago, versus 9% in the last survey conducted in October.

This was the highest proportion since the quarterly survey began 11 years ago, Deloitte said.

"The fog of uncertainty that has lingered over the UK since the 2016 EU referendum is lifting. CFOs ... are beginning 2020 with sentiment levels that would have been unimaginable at any time in the last three years," Deloitte chief economist Ian Stewart said.

Just over half of chief financial officers said they expected revenues to rise over the next year, up from 18% three months ago, and 38% said they planned to invest more, the highest proportion in four years.

Some two thirds of CFOs said they expected Brexit to damage the business conditions, down from more than four fifths earlier in 2019. Weak domestic demand was the biggest risk, according to CFOs, though it was less of a worry than three months earlier.