The government is facing a bigger-than-expected hole in the public finances as it prepares for next month's Budget.
A downgrade to the UK's productivity performance from the government's official forecaster could lead to the chancellor facing a £20bn gap in meeting her tax and spending rules, the BBC understands.
Rachel Reeves has confirmed both tax rises and spending cuts are options in next month's Budget.
The Treasury declined to comment on "speculation" ahead of the Office for Budget Responsibility's (OBR) final forecast, which will be published on 26 November alongside the Budget.
The OBR will deliver its final draft forecast, including productivity - a measure of the output of the economy per hour worked - to the Treasury on Friday.
