THE HAGUE (AFP) - A Greenpeace employee has been fired after losing the environmental charity 3.8 million euros (S$6.4 million) in a failed gamble on international currency markets, the group said on Sunday.

"Nothing suggests at this point that he acted for personal gain, it seems to be a terrible miscalculation," Greenpeace communications director Mike Townsley told AFP.

The unnamed employee "went above his authority" in agreeing the deal with a broker who was meant to mitigate currency losses for the charity, he said.

"The contract turned out to be a very bad one," Mr Townsley said, adding that an internal investigation is underway.

Netherlands-based Greenpeace, like many big charities, agrees fixed-rate foreign exchange deals with third-party brokers to try to protect themselves from world currency fluctuations.

"It is common practice for organisations like ours, with a worldwide presence," Mr Townsley said.

"We would be too exposed to currency fluctuations and risk to lose a lot of money."

Greenpeace, known for its militant anti-drilling campaigns at oil rigs in the Arctic, has a total annual budget of around 300 million euros.

No Greenpeace campaign will suffer as a result of the loss, which will be absorbed by reducing expenses such as infrastructure over the next two to three years.

"We would like to apologise" to donors, Mr Townsley said.

"We will do whatever it takes to make sure it doesn't happen again."