Police said most of the thefts in the ACT were opportunistic but there were sophisticated gangs at work throughout Australia estimated to be costing up to $100million a year.

The largest haul recovered so far was in March when 30 tonnes of copper with an estimated value of more than $2.4million was found in a container in Melbourne.

In the ACT, in the period from July last year until May, there were about 40 incidents valued at $240,000 reported, the chairman of ACT Crime Stoppers, Bryan Roach, said.

The largest theft, in June 2007, was of $155,000 of copper cabling and piping stolen from a site in Deakin.

Mr Roach said the thefts frequently took place at development sites before cables were connected. Some of the most audacious thefts included the cutting down of 16 power poles and the removal of 4.2km of power lines in the Blue Mountains in May and the theft of a modernist sculpture by Gerald Lewers from the front of the Penrith Regional Gallery. In Melbourne, a church bell has been stolen, along with bronze taps from schools and vases from cemeteries.

In Britain, the illegal trade in copper and other metals such as brass and aluminium is estimated to be worth up to $750million a year. Three years ago thieves used a crane to steal a Henry Moore statue valued at more than $7million. The theft of metal from railways has also caused thousands of hours of delays in Britain. And in London, tens of thousands of manhole covers go missing each year and last year more than 400,000 aluminium beer kegs were stolen.

In Philadelphia in the US, 2500 manhole covers were stolen over the past year and a young girl was injured after falling into an uncovered 2m-deep drain.

It is believed most of the copper stolen in Australia is sold to scrap merchants, although a significant amount is exported to Asia.