The concern has come over the proposed EU Optical Radiation Directive, which it says, would leave employers liable for skin cancers suffered by their workers even though the cancer may not be caused by occupational exposure to the sun.
European politicians will vote on the directive on September 6.
FMB external affairs director Andrew Large said: 'Skin cancer is a serious matter, and the FMB would encourage construction workers to cover-up in the sun, but while the EU directive is well-intentioned, it is totally unenforceable.
'The proposed requirement for employers to regulate their workers' exposure to sunlight is completely impractical. Requiring them to do so would not only cause great difficulty to tens of thousands of construction businesses in the UK, it would also make them liable for something over which they have little control.'