More than a quarter of the construction sites visited in Greater Manchester last week failed safety inspections.
Health and Safety Executive (HSE) inspectors carried out checks at 163 construction sites in Manchester, Salford and Trafford during two days of intensive inspections.
They issued a total of 56 enforcement notices at 42 sites, either stopping work immediately or requiring improvements to be made. Some construction companies may face being prosecuted.
Inspectors also visited 15 sites in Warrington during the intensive inspections on 10 and 11 March but did not issue any enforcement notices in the borough.
Nearly half of the enforcement notices concerned unsafe work being carried out at height. Other issues included dust, unsafe electrics and the general state of sites.
Polly Tomlinson, HSE's principal inspector for construction in Greater Manchester, said: "The majority of the construction sites our inspectors visited had good health and safety procedures in place. But the other 42 sites are letting the rest of the industry down and putting workers' lives at risk.
"We will continue to make unannounced visits to sites, and take enforcement action when necessary, until the message gets across. It simply isn't worth taking risks to try and save money."
Newly released figures from HSE show there were 498 serious injuries and one death on construction sites in Greater Manchester last year. There were also 45 serious injuries and one death in Warrington.
The intensive inspections took place as part of a month-long initiative aimed at stopping dangerous practices on building sites across Great Britain.
HSE wants to raise awareness of construction site risks to prevent deaths and injuries in the future. Construction is one of Britain's most dangerous industries, with five deaths and 1,339 serious injuries in the North West during 2008/9.
The national inspection initiative is focusing on refurbishment, including roofing work. Inspectors are making unannounced visits to ensure that sites are managing refurbishment work, including work at height, safely and that sites are in good order.
Last year, inspectors visited 274 sites across the region and issued 97 enforcement notices during a similar month-long initiative.