Sir Keir Starmer will back the Budget and vow to go "further and faster" on growth amid claims Rachel Reeves misled voters over the scale of fiscal challenge.

Reeves had claimed the a downgrade to the UK's economic productivity would make it harder to meet her own fiscal rules. Pre-Budget speculation stated she faced as much as a £20bn gap in meeting her fiscal rules.

But the Office for Budget Responsibility (OBR) on Friday said it had informed the Chancellor as early as September 17 that an improved tax take from growing wages and inflation meant the shortfall was likely smaller than initially expected, and told her in October it had been eliminated altogether.

In a bid to defend his Chancellor, Starmer will say "economic growth is beating the forecasts", but that the Government must go "further and faster" to encourage it.

He will also unveil new reforms to building nuclear power station to cut red tape.