Chancellor Rachel Reeves could be facing an additional £20billion gap in public finances after a downgrade in the UK's productivity performance.
Data from the Office for Budget Responsibility (OBR) will deliver its final draft forecast to the government on Friday, which is expected to show a continuation of long-running poor productivity.
The BBC understands the figures could lead to an extra £20billion gap in public funds ahead of Reeves' autumn budget.
The Treasury said it would not comment on "speculation" before the OBR's final forecast is published on November 26.
It comes after the OBR previously predicted a partial recovery in productivity growth - but it failed to materialise.
Calculations from the Institute of Fiscal Studies shows that for each 0.1% downgrade in productivity forecast, public sector net borrowing will increase by £7billion in 2029-30. That would mean a 0.3% cut could add £21billion to the budget gap.
Read the full story on the BBC website.
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