Britain's economy will grow far more slowly than expected over the next five years, as it faces Brexit uncertainty and weak productivity, finance minister Philip Hammond said Wednesday.

Gross domestic product will grow 1.5 percent this year, by 1.4 percent in 2018, 1.3 percent in both 2019 and 2020 and 1.5 percent in 2021, Hammond revealed in a raft of forecast downgrades included in his annual budget.