The head of the UK’s official statistics watchdog has challenged Rishi Sunak over his claim to have reduced public debt, saying the prime minister’s definition of this was so specific and limited that it risked being misleading for voters.

Sir Robert Chote, the chair of the UK Statistics Authority (UKSA), said Sunak’s claims last month “may have undermined trust in the government’s use of statistics and quantitative analysis in this area”.

Writing to Sarah Olney, the Liberal Democrats’ Treasury spokesperson, Chote said the Office for Statistics Regulation, the UKSA’s regulatory arm, would “work with the prime minister’s office to ensure further statements on debt levels adhere to our guidance on intelligent transparency”.