MTV presenter and comedian James Barr said "Jack Whitehall is amazing" and called the move a "huge moment for the LGBTQ+ community" but labelled it "frustrating to cast NonGay people in gay roles".
Actor Ethan Harvey tweeted: "If only there were gay actors who could play "camp" as well as Jack Whitehall".
"Really @Disney #JungleCruise? Your first significant gay role will be played by a straight white man perpetuating stereotypes? Fail! This ship should sink".More news: Google tracks your movements even if you’ve turned location history off
Though Disney has stirred up rumors of gay characters like Josh Gad's LeFou in the live-action Beauty and the Beast, the entertainment giant has reportedly never featured an openly gay character in any of their films.
Chris Salvatore, an actor and singer, wrote: "Such a damn shame it's so hard to find gay actors to play gay roles in Hollywood".
Jungle Cruise, which is based on a Disney theme park ride of the same name, is due to be released in October 2019.
"It's that there are so many gay actors that are under represented in all sorts of roles across the board. and so I think that this is, fantastic, but also a bit sad".More news: Trump endorses call for boycott of Harley-Davidson motorcycles
However, gay MP for the UK's Labour Party Wes Streeting, was more positive about the selection, posting: "Shock as actor is asked to play someone different from themselves".
Disney chiefs are yet to respond to the backlash.
The controversy comes a few days after Australian actor Ruby Rose left Twitter amid backlash for "not being gay enough" to play out lesbian superhero Batwoman on the DC TV series Arrow.More news: Many injured as vehicle crashes into barriers outside United Kingdom parliament