No, that would require a change in the law. Subsection 5(iii)(b) of the The Budget Responsibility and National Audit Act 2011 states that the OBR must not consider alternative policies, which restricts us to assessing the likely impact of the current policies of the current Government. Official independent fiscal institutions do fulfil this role in some other countries, notably the CPB Bureau of Economic Policy Analysis in the Netherlands. Parliament did discuss whether the OBR should play this role in 2014 and we wrote to the Treasury Select Committee to set out some of the issues that would need to be addressed if ever we were to be asked to do so. The Treasury’s 2015 review of the OBR considered the issue again. It recommended that the law should not be changed to allow us to perform this role.
"It is the duty of the Office to examine and report on the sustainability of the public finances"