The HSE carried out the intensive inspection campaign on the refurbishment sector in Sefton, Merseyside, with a focus on the towns of Southport, Crosby and Bootle.
Of the 15 sites visited by inspectors, enforcement action was taken on 13.
Seven prohibition notices were issued to halt work on sites immediately and another six improvement notices were also served.
Infringement of working at height safety rules accounted for the majority of the notices, the HSE said, with dangerous and untidy sites also a significant problem.
Inspector Susan Ritchie said: "I was dismayed to find that 13 enforcement notices were issued in one day when we inspected just 15 sites. This is unacceptable.”
She said while the inappropriate use of ladders on construction sites was happening less frequently, many of the access towers and scaffolds used instead were found to be unsafe, without proper hand rails or toe boards.
Ms Ritchie added: "There remains a lot of work to be done to improve safety standard in the construction industry in Sefton and the Health and Safety Executive are determined to drive up standards.”