Markit's and the Chartered Institute of Purchasing & Supply's construction purchasing managers' index (PMI) for the U.K. dropped to 51.2 in May from 52.0 in April. It was the lowest level since June 2013.

Analysts had expected the index to remain unchanged at 52.0.

A reading above 50 indicates expansion in the construction sector.

The decline was mainly driven by a drop in new orders.

"Construction companies are facing a challenging second quarter of 2016, with growth headwinds apparent across all three key areas of activity," Senior Economist at Markit, Tim Moore, said.

"May data signalled the worst month for commercial building since June 2013, while residential work and civil engineering activity both saw a renewed loss of momentum," he added.