3-4 minutes - Source: BBC
The Office for National Statistics (ONS) revised down its previous estimate of a 2% contraction, with all the main economic sectors dropping.
There was a significant economic impact in March, as the coronavirus pandemic began to have an effect.
The data comes as the prime minister is set for a major speech on the economy.
Jonathan Athow, deputy national statistician at the ONS, said: "Our more detailed picture of the economy in the first quarter showed GDP shrank a little more than first estimated.
"Information from government showed health activities declined more than we previously showed.
"All main sectors of the economy shrank significantly in March as the effects of the pandemic hit."
The first-quarter contraction is now the joint biggest drop since the July-to-September period in 1979.
Mr Athow said: "The sharp fall in consumer spending at the end of March led to a notable increase in households' savings."
When compared with the same three-month period a year ago, the economy shrank by 1.7%, worse than the previous estimate of a 1.6% contraction.
But with the coronavirus lockdown only coming into force on 23 March, the second quarter will show the full hit on the economy.
Recent ONS monthly figures showed the economy plummeted by 20.4% in April - the largest drop in a single month since records began.
That contraction was three times greater than the decline seen during the whole of the 2008 to 2009 economic downturn.
Samuel Tombs, chief UK economist at Pantheon Macroeconomics, said the latest figures could be summed up in one line: "The biggest contraction for 40 years, even though Q1 contained just nine lockdown days."
The data "was just the prelude" to the worse to come, he added.
Later on Tuesday, Boris Johnson is set to make a keynote speech on the economy with a promise to "build back better".
Speaking in the West Midlands, the prime minister will say he wants to use the coronavirus crisis "to tackle this country's great unresolved challenges".
As part of what he is expected to call a "new deal", Mr Johnson will set out plans to accelerate £5bn of spending on infrastructure projects.