More than 160,000 people have told HM Revenue and Customs to delete biometric data it gathered during phone calls.
Following an investigation and campaign by Big Brother Watch, HMRC now gives people the option to delete the voiceprints taken.
The tax authority captured millions of callers’ voice data after launching its Voice ID system in 2017, but originally gave people no way to opt out.
Big Brother Watch said the tax authority had “created one of the largest known state-held voice databases in the world”.
“It is down to the ICO to take robust action and show that the government isn’t above the law,” Big Brother Watch said in a statement.