The contraction also comes amid a record fall in manufacturing output and major losses in financial services.
Many analysts were shocked at the size of the second-quarter contraction.
The minutes of the Bank of England's (BoE) July meeting, published on Wednesday, had suggested the near-term outlook for the economy was brighter than the central bank had predicted in May, not worse.
The decline in the UK economy, which has now shrunk for five consecutive quarters,
is more than double the drop seen in the early 1990s recession and not far off the six per cent contraction experienced in the early 1980s.
David Blanchflower, a former policymaker at the BoE who left the central bank in May, said: "The talk of green shoots had lulled people into a false sense of security."
Blanchflower, who was the only person on the bank's interest rate-setting committee to predict the current recession, said the bank could not afford to call a halt to its asset-buying programme to pump money into the economy.
"The end-game for quantitative easing (QE) is a long way off," he said.
"The BoE needs to expand QE a lot right now because otherwise any recovery will take an awfully long time."
The bank has already cut interest rates to a record low of 0.5 per cent and has pumped close to $200bn of new money into the economy in order to pull the country out of recession and promote lending.
Policymakers will debate next month whether more stimulus is needed.