LONDON (CNNMoney) - Britain's economy is running out of momentum.
The Office of Budget Responsibility slashed its economic growth forecast for 2017 to just 1.5% on Wednesday, down from an estimate of 2% in March.
The independent fiscal watchdog said the pain would extend until at least the end of the decade, with growth slowing to 1.4% next year and 1.3% in 2019 and 2020.
In a statement, the group said it expects growth to slow "as public spending cuts intensify and Brexit-related uncertainty continues to bear down on activity."
The sharp downgrades underscore the difficult economic conditions under which Britain will depart the European Union, where growth is forecast to hit 2.3% in 2017 and 2.1% in 2018.
U.K. Treasury chief Philip Hammond announced the downbeat forecasts during his budget speech, a major event on the country's political calendar.
The pound dropped against major currencies as the speech was delivered.
Business investment has slowed in Britain because of uncertainty over Brexit.
The pound has slumped 12% against the dollar since the referendum vote in June 2016, fueling inflation that recently hit 3%.
Consumer spending fell the most in four years in October, according to data from Visa.