This article is more than 1 year old

This article is more than 1 year old

Economic growth in Britain is expected to slow to the lowest levels since the financial crisis as firms run down Brexit stockpiles, according to a leading business lobby group.

After a stockpiling rush this year that pumped up the rate of economic growth, the British Chambers of Commerce said growth would slow in 2020 and 2021.

The organisation has slashed its forecast for GDP growth next year to just 1%, from 1.3%, marking the weakest expansion in the British economy since the 2009 recession that followed the financial crisis.

Growth is also forecast to remain subdued in 2021, at 1.2%, down from its previous estimate of 1.4%.

The British economy has benefited in recent months as companies braced for a no-deal Brexit ahead of the original deadline of 29 March, before Theresa May delayed the process until the autumn.

Q&A What is gross domestic product (GDP)? Show Hide Gross domestic product (GDP) measures the total value of activity in the economy over a given period of time. Put simply, if GDP is up on the previous three months, the economy is growing; if it is down, it is contracting. Two or more consecutive quarters of contraction are considered to be a recession. GDP is the sum of all goods and services produced in the economy, including the service sector, manufacturing, construction, energy, agriculture and government. Several key activities are not counted, such as unpaid work in the home. The ONS uses three measures that should, in theory, add up to the same number. • The value of all goods and services produced – known as the output or production measure.

• The value of the income generated from company profits and wages – known as the income measure.

• The value of goods and services purchased by households, government, business (in terms of investment in machinery and buildings) and from overseas – known as the expenditure measure. Economists are concerned with the real rate of change of GDP, which accounts for how the economy is performing after inflation. Britain's government statistics body, the Office for National Statistics, produces GDP figures on a monthly basis about six weeks after the end of the month. It compares the change in GDP month on month, as well as over a three-month period. The ONS warns that changes on the month can prove volatile, preferring to assess economic performance over a three-month period as the wider period can smooth over irregularities. The most closely watched GDP figures are for the four quarters of the year; for the three months to March, June, September and December. The figures are usually revised in subsequent months as more data from businesses and the government becomes available.

The ONS also calculates the size of the UK economy relative to the number of people living here. GDP per capita shows whether we are actually getting richer or poorer, by stripping out the impact of population changes. Richard Partington

The unprecedented rise in manufacturers storing up raw materials and components fuelled a rise in GDP of 0.5% in the first three months of the year, which the BCC said should lift the overall growth rate in for 2019 as a whole.

However, the increase means firms now have inventories they can run down without needing to place as many orders for new stock, hitting economic momentum. Economic growth went into reverse in April as companies halted their rush to stockpile, while car manufacturers also halted production after planning to avoid disruption around the original Brexit deadline.

Suren Thiru, head of economics at the BCC, said: “It is increasingly likely that the temporary boost from historically high stockpiling in the first quarter, which has marginally improved the growth outlook for this year, will be surpassed over the medium-term by the negative impact from the running down of these inventories.”

He said a no-deal Brexit could damage economic growth in Britain further, should a new prime minister after the Conservative leadership race walk the country away from a deal with Brussels.

“A messy and disorderly exit from the EU remains the main downside risk to the UK’s economic outlook as the disruption caused would increase the likelihood of the UK’s weak growth trajectory translating into a more pronounced deterioration in economic conditions,” he said.

Sign up to the daily Business Today email or follow Guardian Business on Twitter at @BusinessDesk

The continuing lack of clarity over Brexit means that business investment is forecast to contract at a faster rate this year than was previously thought, while the lingering uncertainty means corporate spending will also recover more slowly next year.

Business investment fell for four quarters in a row last year, marking the worst run in Britain since the financial crisis, and damaging the longer-term growth rate of the UK economy. Companies investing in new technology have the potential to produce gains in productivity.

The BCC said business investment was expected to continue falling in 2019 due to the political chaos over Brexit.

Adam Marshall, director general of the lobby group, said: “Businesses are putting resources into contingency plans, such as stockpiling, rather than investing in ventures that would positively contribute to long-term economic growth. This is simply not sustainable.”