The UK economy is expected to grow by 1.2 per cent in 2020, according to a new survey by the consultancy Yougov.
That is down from 1.5 per cent growth in the second quarter.
The government said it would boost public spending to 0.5pc of gross domestic product by 2020.
The economy is predicted to grow 0.4 per cent this year, down from 2.4pc growth in 2017.
Inflation is expected at 1.9pc this year.
The survey also suggested the UK could see another big year of economic growth in 2020.
It showed that the economy is projected to expand by 1 per cent, up from 1 per, in 2020 and 2.7 per cent by 2021.
However, it also said it was “potentially more volatile” than other major economies.
It is unclear whether the economy would grow as much in 2021 as it did in 2020 due to the strong dollar and a slump in oil prices.
“The UK economy was hit hard by Brexit and uncertainty surrounding Brexit has continued to have an impact on the economy and it is not clear whether the UK would be able to sustain a sustained growth rate in 2021,” Yougov said.
The UK has the third-biggest economy in the world behind Germany and France.
It was also the first of the big emerging economies to report weak economic growth.
The US had the second-bigest economy in 2021, followed by India, Brazil and South Korea.
The Economist Intelligence Unit (EIU) said that despite the weak performance, the UK was likely to achieve growth of 1.7pc in 2020 as compared with 1.6pc in 2017, a figure that would be a “remarkable achievement”.
“The headline GDP growth figure was a much lower figure than the government had initially forecast, but it is still much more than the 1.3pc growth we expected,” EIU UK economist Richard Porter said.
“This would suggest the UK can be a very strong economy in 2018.”
There is still uncertainty over the outcome of the Brexit vote and the uncertainty about Brexit’s impact on growth will be exacerbated by the weaker pound,” he said.
Mr Porter said that the UK had a strong position on the Eurozone, which is a trading bloc but which is not a member of the single currency.
He said: “The Brexit vote means that the Euro is less likely to be a global currency and that means the UK has a strong ability to influence its own policies, including the Brexit negotiations.”
The British government’s economic forecasts for 2020 were set out in the government’s first economic outlook since the referendum, published last October. “
We have a strong relationship with both sides of the EU, both of which are committed to our common values,” he added.
The British government’s economic forecasts for 2020 were set out in the government’s first economic outlook since the referendum, published last October.
The Economic Secretary to the Treasury, Greg Clark, said that Brexit had hurt the economy.
He told the Financial Times: “It was a major shock to the economy that the pound collapsed against the euro.”
The economic outlook for 2020 was a very positive one, it was stronger than it was in 2017 but it was weaker than it had been in any of the previous three years.
“He added that there was “much room” for the economy to recover from Brexit.
He added: “I think we will have a very resilient economic environment in 2020.”
He also said the government would announce a series of measures to boost growth, including by providing more funding for infrastructure, reducing corporation tax, and extending a state pension.