Rachel Reeves must cope with lower growth and higher borrowing costs this year, as the Treasury’s independent forecaster said the global economic situation was more unpredictable and could worsen if Donald Trump imposed significant trade tariffs. In a report to coincide with the chancellor’s spring statement, the Office for Budget Responsibility (OBR) said the economic outlook was “more challenging” and “more uncertain” as it forecast that growth would halve this year to 1% from its 2% prediction at the time of October’s budget. After Reeves slashed welfare benefits and prepared big departmental spending cuts to claw back £14bn of savings