Animal rights group PETA has become a shareholder in Thomas Cook so that it can put pressure on fellow shareholders and executives to stop selling tickets to SeaWorld.
PETA US has invested in the travel giant specifically so its representatives can attend annual general meetings.
PETA director Elisa Allen said: "As a shareholder, PETA US will be able to push its management to do the responsible thing for shareholders and animals alike and cut ties with SeaWorld."
The activist group said Thomas Cook has this week removed all online promotions of SeaWorld, but it wants the company to go one step further and stop all ticket sales.
Since August 2017, PETA says it has led protests outside more than 100 Thomas Cook locations across the UK and prompted more than 20,000 people, including Sharon Osbourne and Paul O’Grady, to write to the company to urge it to stop selling tickets.
Thomas Cook said it was surprised by PETA’s approach.
"As the first tour operator to enforce an animal welfare policy by removing from sale animal excursions that don’t meet the standards we require, Thomas Cook welcomes discussion on this important topic," it said in a statement.
"We have been encouraged by the support we’ve received from groups like World Cetecean Alliance, however we’re surprised by PETA’s approach.
"This appears to criticise us specifically because we’ve taken an industry-leading position. We are committed to continue to work with the industry to raise standards of animal welfare around the world."
