The UK’s statistics watchdog has closed an investigation into remarks made by an official about the economy “going gangbusters” that were cited by Rishi Sunak.

It was looking into the comments made by chief economist of the Office for National Statistics (ONS) last month amid concerns that politicians could misuse economic data in the run-up to the election.

Grant Fitzner used the phrase in a briefing with journalists on 10 May after figures showed the UK was officially out of recession and that the economy grew by 0.6% in the first three months of the year and became the basis of a Daily Mail front page story the following day.

A week later Sunak, in an interview on the Radio 4 Today programme, repeated the words, telling listeners: “The facts are the facts. You had, I think, the person from the Office for National Statistics talking about the economic growth that the country produced in the first quarter of the year. He said what he said about that and I think he used the term ‘gangbusters’, so I will leave it at that.”

The UK Statistics Authority, chaired by Sir Robert Chote, said on Tuesday that it was investigating the remarks. However, the case was examined by a different watchdog, the Office for Statistics Regulation (OSR), which looked only at the ONS use of the term and not Sunak’s.

The OSR reported on Thursday that it had closed the case, but did not provide any further information on its findings, beyond referring the Guardian to a statement from the ONS, which said: “The use of the word ‘gangbusters’ was a passing reference used when our chief economist was discussing the first quarter’s economic growth with journalists at our press briefing on release day.

“The reference was made – paraphrasing a remark by a former Australian prime minister – as [first quarter] growth had come in stronger than commentators expected, with broad-based growth across services and manufacturing industries, and with quarterly growth at its strongest pace since the pandemic.

“It was certainly not intended as a comment about the overall state of the economy and when the comment was made it was immediately clarified to those present that this was not a word that the ONS would use to describe the first quarter’s growth. We also put the comment in context for journalists who followed up afterwards.”

Dario Perkins, a senior economist at the consultancy TS Lombard and former Treasury official, said it was unwise for the ONS to say the economy was growing quickly and wrong for the prime minister to use one quarter of GDP growth to argue that economic health had been restored.

“The ONS is not supposed to use these kinds of descriptive words to tell a story about the economy. And it is also wrong to say the economy is booming in the first three months of the year when we have only just recovered lost growth from last year’s recession and suffered the worst incomes squeeze in a generation.”

The OSR intervention came hours after Chote began a review of Sunak’s claim in Tuesday night’s leaders debate that independent civil servants calculated that Labour would raise taxes by £2,000 for everyone should it win the election on 4 July.

Labour has complained that the figure was wrong and was erroneously described as independently verified by Treasury civil servants.

On Tuesday, hours before the TV debate between Sunak and Labour leader Keir Starmer, Chote wrote to the main political parties and top civil servants to warn them about “ensuring the appropriate and transparent use of statistics”.

Chote previously ran the Office for Budget Responsibility, the Treasury’s independent forecaster, and was the head of the Institute for Fiscal Studies thinktank, a leading arbiter of government tax and spending policies.

On Thursday, the UK Statistics Authority said the £2,000 claim failed an “intelligent transparency” test and was misleading. It warned all parties to refrain from making exaggerated or misleading claims about tax and spending policies.

• This article was updated on 6 June 2024 to replace an earlier version that carried the headline: “UK statistics watchdog to investigate Sunak’s use of term ‘economy going gangbusters’”. The investigation by the UK Statistics Authority concerned remarks made by an ONS official during a briefing with journalists, not the repetition of those remarks by Rishi Sunak, as the previous version stated. This investigation was not personally carried out by Sir Robert Chote but, as the updated version makes clear, by the Office for Statistics Regulation.