The Greenpeace flagship Rainbow Warrior is currently transiting from Mauritius to the Maldives as part of its Indian Ocean expedition and found in total three fishing boats deep within the Chagos marine protected area, established by the UK government in 2010.

Onboard one vessel, identified as IMUL-A-0352KLT, Greenpeace found dozens of sharks, including thresher sharks, a protected species in this region. This boat is not on the Indian Ocean Tuna Commission (IOTC) list of registered vessels and is illegal.

A second boat, identified as IMUL-A-12939MTR, was not on the IOTC list either and is illegal. Greenpeace also boarded that vessel, mainly finding skipjack tuna.

These fishing boats use indiscriminate gillnets and longlines to catch sharks, tuna and other marine life.

"We are demanding the UK government inspect these vessels and actively protect the marine reserve from illegal fishing. Without enforcement this protected area is not worth the paper it is written on," said Greenpeace UK oceans campaigner Simon Clydesdale on board the Rainbow Warrior.

Greenpeace has given the details of the vessels to the regional authorities as well as the Foreign Office in London, urging Britain to send its patrol vessel the Pacific Marlin out from the nearby US military base Diego Garcia, where it was believed to be at anchor on Tuesday, to inspect the three vessels.

Greenpeace encountered a third vessel, identified as IMUL-A-0341KLT. This boat was authorised to fish in the region but not inside the Chagos protected area.

'Illegal fishing is a massive problem in the Indian Ocean. It is stealing from coastal communities and plunders marine life such as sharks. Boats that repeatedly fail to comply with the rules must be stopped. Our oceans need fewer fishing vessels that are properly controlled if we are to reverse the current overfishing crisis," said Greenpeace International oceans campaigner Sari Tolvanen.

Greenpeace is calling on key market players and tuna brands to ensure they have a traceable supply chain and only source tuna that is legal and comes from sustainable sources.

The Rainbow Warrior is continuing its mission in the Indian Ocean to highlight the problems associated with excessive tuna fishing, unsustainable fishing practices, and the need for countries to cooperate and ensure that communities will benefit from the wealth coming from the oceans in the future.