The chancellor has pledged to spend a £26.6bn Brexit war chest to boost the economy, if MPs vote to leave the European Union with a deal.
Philip Hammond vowed to free up more money to cut taxes and spend on public services in a "deal dividend".
However, he said these spending plans were based on a smooth Brexit.
Mr Hammond used his Spring Statement to warn that a disorderly Brexit would deal a "significant" blow to economic activity in the short term.
He said the decision by MPs to reject Theresa May's Brexit deal for a second time had left a "a cloud of uncertainty hanging over our economy".