"We and other insurers are experiencing significantly increased claims activity including six figure losses on metals which historically have not been particularly attractive to thieves and have therefore had limited security and protection.
"It is crucial that business and property owners remain vigilant when it comes to protecting their metal stocks and trade process components."
Materials theft has risen by as much as 120% in some parts of the UK over the past year.
International metals prices have rocketed in response to demand from boom economies like India and China.
The rail network has been hardest hit. In 2006/7 Network Rail reported more than 1,000 incidents of cable theft, costing it more than £4M and causing 243,717 delay minutes.
This was significantly up from the year before when there were just 50,021 minutes delay due to cable theft.
In Ukraine, thieves took an entire 11m long, steel bridge weighing 1t that spanned the Svalyavka river.
British Transport Police Assistant Chief Constable of the Paul Crowther said metal theft was the biggest challenge faced by his force after terrorism.
His teams are employing a series of hi-tech and traditional measures to deal with the problem.
Crowther appealed to contractors to report the movements of suspicious individuals.
- If you have information about stolen metals to contact Crimestoppers on 0800 555 111 or the British Transport Police dedicated metals theft hotline on 0800 405 040.