Tax revenue would be £150bn higher if British GDP had grown at the rate of the US since 2008

UK nominal tax revenue with US productivity growth

This assumes that tax (National Accounts) as a percentage of GDP remains the same in both scenarios. Some of this additional revenue would need to be spent addressing Baumol effects to maintain existing public service provision and on increasing earnings-linked welfare benefits.
Chart: Centre for British ProgressSource: OBR, OECDGet the dataCreated with Datawrapper