Cook launched a range of package holidays to the Chinese beach resort, situated in Hainan province, last month, after signing a strategic partnership to develop the destination.

It has since been criticised for selling trips to the recently opened resort, despite announcing it was dropping SeaWorld and any attraction which featured captive orcas.

Atlantis, owned by Chinese conglomerate Fosun which also has stake in Cook, does not keep orcas but does house Bottlenose dolphins, white sided dolphins, sea lions and beluga whales for display and entertainment.

Cook launched a review of its animal welfare policy 18 months ago to ensure any animal attractions it sells are 100% compliant with Abta’s animal welfare standards.

In a blog post entitled ‘Thomas Cook: Goodbye orcas, hello belugas?’, Dolphin Freedom UK wrote: “The market in China not only exploits dolphins, but also exploits beluga whales and orcas too.

"Dolphin Freedom believe this is a very tangible admission by Thomas Cook to show that they are supporting the new marine park industry in China and the confinement of beluga whales.”

The group said it had written to Cook’s environmental manager following concerns the company was promoting beluga captivity and a new dolphinarium market in China.

Dolphin Freedom UK said it had since received a response from Cook “immediately” and that the operator was “investigating” the concern.

“It is well documented that the marine captivity industry is notorious for a lack of transparency so we very much welcome Thomas Cook’s correspondence and look forward to their reply,” the blog said.

A spokesperson from Cook added: “Thomas Cook takes the welfare of animals in captivity very seriously. We are the only tour operator to audit all of the animal attractions we sell and, as a result of this audit process, have removed 29 attractions in the last 18 months which didn’t meet the minimum Abta animal welfare standards that we insist upon.

“In addition, we are the first major holiday company to announce that we are going to stop selling excursions which keep Orcas in captivity – a bold decision and one that is in keeping with our leadership position in this area. We will continue to insist that all animal attractions we sell undergo an audit under our rolling programme of audits conducted by an independent provider.

“This will include the Atlantis Sanya, only recently opened. We will also continue to review our animal welfare policy and use our voice to promote a transition away from traditional animal attractions towards more sustainable alternatives.”