Placer Dome owned 39.9 percent of Marcopper until 1997, a year after the mine was shut after a drainage tunnel burst, pumping millions of tonnes of mine waste into the Boac River on the island located 150 km (94 miles) south of Manila.

Three years earlier, in 1993, a Marcopper mine dam had collapsed, releasing "a flood of metal-enriched silt" into another local river, Oxfam said.

"For more than 20 years, Marcopper dumped millions of tonnes of toxic mine waste in Marinduque's seas and polluted its rivers," Oxfam said in the 44-page document.

"As a result, people have lost their health, livelihoods and some have even lost their lives," it said.

Placer Dome spokeswoman Meghan Brown said the company, which is the world's fifth biggest gold producer, had not seen Tuesday's Oxfam release. But she sent Reuters two letters that the miner had previously sent the aid group, as well as a company backgrounder on its involvement with Marcopper.

The Vancouver, British Columbia-based company said in the documents that it agreed with Marcopper and its controlling shareholder, F Holdings, in 2001 that F Holdings would clean up the Boac River system, with money supplied by Placer Dome.

The firm also said it paid a further $70 million to plug the tunnel, clean the river and help Marcopper repay its debt.

Another $1.5 million was paid in compensation to residents, it said, and a further $735,000 could still be paid.

The company said its "voluntary involvement" with the clean-up of the 1996 tailings spill "is concluded" and told Oxfam to contact mine owner Marcopper. Oxfam said it was "difficult" to figure out who owns Marcopper and F Holdings.

The Oxfam report has been in the works since May 2002, when it said Marinduque residents asked it to take up their case. Oxfam is the latest in a list of environmental and nongovernmental organizations to take on their concerns.

The report comes at a time when the Philippines government is rolling out a welcome mat to foreign mining investors. In December the Supreme Court reversed a ruling barring foreign companies from taking a 100 percent stake in mining projects.