HSE inspectors visited 3,237 sites and saw 4,080 contractors.
During the blitz, 581 sites were found to have practices that put workers at risk with a total of 870 enforcement notices issued and in 603 instances work had to stop immediately.
Notices were served on 18% of sites compared to 22% in a similar initiative last year.
Philip White, Chief Inspector of Construction, said: “It is encouraging that inspectors found a slight improvement in standards and small construction firms are taking safety seriously when carrying out refurbishment work.
“But this is just a snapshot, and the number of notices served for unsafe work at height is still unacceptable, particularly when the safety measures are well-known and straightforward to implement.
“Too many contractors continue to put their own or other people’s lives at risk and we will not hesitate to take action where standards are not met.”
Inspectors targeted sites where refurbishment or repair work was being carried out.