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The cross-party Commons Treasury committee has expressed concerns about reports that Liz Truss, the frontrunner in the Tory leadership contest, may hold an emergency budget in September without asking the Office for Budget Responsibility to update its fiscal and economic forecast.

The OBR usually publishes a new forecast alongside a budget, and it provides an independent assessment of what impact the budget measures will have. The system was put in place by George Osborne to discourage the Treasury from making dubious claims about what its tax and spending announcements might be able to achieve.

OBR forecasts provide transparency and reassurance to the markets on the health of the nation’s finances. As a committee, we expect the Treasury to be supporting and enabling the OBR to publish an independent forecast at the time of any significant fiscal event, especially where, unlike other recent fiscal interventions, this might include significant permanent tax cuts.

Whether such an event is actually called a budget or not is immaterial. The reassurance of independent forecasting is vital in these economically turbulent times. To bring in significant tax cuts without a forecast would be ill advised. It is effectively ‘flying blind’.