Optimism amongst finance chiefs of the UK's largest businesses has rebounded, according to Deloitte's latest CFO survey published on Thursday.

The 38th quarterly survey revealed that 27% of the CFOs were more optimistic about the future prospects for their companies, which was better than 16% in the previous quarter and up from the 3% that showed optimism immediately after the EU referendum. The current reading, Deloitte said, marked an 18-month high.

Commenting on the survey, Ian Stewart, chief economist at Deloitte, said in a statement, "Buoyed by a backdrop of continued UK growth, CFOs have become markedly more positive on the outlook for their businesses and enter 2017 in better spirits than at any time in the last 18 months.

"However, rising optimism does not represent a return to business as usual. Uncertainty in the external environment continues to keep a lid on corporate expansion. Risk appetite remains depressed and is well below average levels and corporates remain on a defensive footing, with cost reduction and building up cash as their top priorities," he said.

Despite this increased confidence, the survey whose respondents included 119 CFOs of FTSE 350 and other large private companies said that uncertainty continued to remain high.

About 89% of the CFOs said they continued to face high levels of economic and financial uncertainty. While this was marginally higher than the 88% in the previous quarter, it was much lower than the 95% seen immediately after the EU referendum.

Another highlight of the survey was that risk appetite remained muted despite increase in confidence. Around 80% of the CFOs said the time was not right to take risks onto their balance sheets. The reading was however better than the 82% seen in Q3 and the 92% after the referendum.

The survey, which took place between 29th November and 12th December, also revealed that Brexit continued to be the biggest business concern.

When asked to weigh such concerns on a scale of 0-100, Brexit was rated 62. This was followed by weak demand in the UK which got a rating of 55. Monetary tightening in the UK and US and weakness in the euro were the next biggest concerns, with respective ratings of 53 and 52.

Majority of the CFOs continued to believe the UK's decision to leave the EU would have a negative impact on the long-term business environment.

The survey findings were not all negative. Improvement was seen in various areas such as expectation on hiring, capital expenditure and M&A activity. About 46% said they expected to reduce capital spending in the next 12 months compared to the 58% reading in Q2. With regards to hiring, 48% said they expect hiring to slow down, better than the 83% in the previous quarter.