"When that failed, they tried to intimidate us, making multiple, intentional approaches to my vessel which resulted in dangerous, near collision situations.
"We have maintained our pursuit for 40 hours in spite of these aggressive, illegal actions, during which time the poachers have been unable to engage in further illegal fishing."
It also managed to chase the Kunlun out of Australia's exclusive economic zone, and into the international waters of the Southern Ocean, Mr Chakravarty said.
It was now following the Kunlun on a northerly course, approximately 2500 nautical miles southwest of Australia.
It was the second aggressive incident towards the Sam Simon in as many days, Sea Shepherd said.
On Monday, the Yongding turned aggressively towards the Sam Simon, crossing within 10m of the conservation ship, narrowly avoiding a collision. It then managed to "split from the chase".
Mr Chakravarty again hit out at the Australian government's lack of action.
"Thanks to the mute response from the Australian government, who maintain an embarrassing silence in the face of this invasion in Australian waters, one more poaching vessel [the Yongding] is now on the loose in the Southern Ocean."
In January both the Kunlun and Yongding, along with the Songhua, were issued with Interpol purple notices for suspected illegal fishing activity and related crimes. The navy was given permission to board the vessels, which were flagged to Equatorial Guinea and were not legally permitted to fish in the region.
But attempts to board them and inspect their catches failed.
Foreign Affairs Minister Murray McCully said two of the vessels had links to a Spanish crime syndicate, Vidal Armadores.
The crew of the HMNZS Wellington captured video evidence of fishermen hauling in Antarctic toothfish - one of the most lucrative catches in the world.
The Southern Ocean fishery, which contains sensitive toothfish and krill populations, is tightly regulated and cannot be fished by countries which do not belong to the 25-member Commission for the Conservation of Antarctic Marine Living Resources.