Fears grow about reliability of ONS data affecting Reeves' budget

Deep problems with the quality of Office for National Statistics data are piling pressure on officials in the run-up to the autumn budget, sources have told the Guardian.

- Anna Isaac Richard Partington

Staff at the Treasury and its independent spending watchdog are struggling to get a clear picture of the UK economy because of troubles at the ONS with producing reliable numbers.

Such is the concern that insiders at the Office for Budget Responsibility believe it may have to again highlight "significant uncertainty" in its forecasts because of poor official data, as it did publicly in March. Economists have warned that the problems risk the chancellor, Rachel Reeves, making tax and spending "missteps".

The OBR forecasts are key to the budget process, as they are used to judge the financial headroom the chancellor has against self-imposed fiscal rules, and form the basis for tax and spending decisions. Its work is also closely watched by financial markets. This can affect the cost of borrowing the government needs to help fund public services.

The ONS, which produces figures on a range of indicators including economic growth, inflation and unemployment that are used by financial markets and government agencies, is struggling with mounting problems as it has delayed or cancelled several of its releases.

Its labour force survey - the official measure of employment in the UK - has been beset with problems amid a collapse in response rates.

On Tuesday, the ONS postponed the release of retail sales figures, due yesterday, for two weeks "to allow for further quality assurance". Household wealth data has also been downgraded and is no longer treated as official owing to quality concerns.