British employers have been on a hiring spree recently, pushing up pay for workers at the quickest pace in a decade, one of the few bright spots for the economy ahead of its departure from the European Union.

Many economists have linked the jobs boom to uncertainty about Brexit which has made employers favour hiring workers -- who can be laid off quickly -- over longer-term commitments to investing in equipment.

The Office for National Statistics said the 2.1% increase in labour costs in the January-March period was weaker than a rise of 3.1% in the fourth quarter of last year.

The ONS also confirmed preliminary data showing a weak picture for productivity in early 2019.

Britain's poor productivity record poses a risk to the country's long-term growth prospects.

Output per hour fell by an annual 0.2% in the January-March period for its third straight fall, the longest such run since 2013 when Britain was struggling to emerge from the hangover of the global financial crisis.

"Our latest figures represent a continuation of the UK's productivity puzzle," said Katherine Kent, head of productivity at the ONS. "This sustained stagnation in productivity in the last decade is at odds with what we've seen after previous economic downturns."