The Office for National Statistics found 23% either did not quarantine at home for 10 days or failed to complete PCR tests on days two and eight.
One in six admitted contacting other people during quarantine, with 62% of these leaving their homes to meet people and 45% having visitors.
The Daily Telegraph said four in 10 were unsure about quarantine rules and 15% mistakenly thought they were permitted to go shopping.
The ONS survey was based on more than 800 unvaccinated adults arriving in the UK in July from amber destinations.
