LOS ANGELES (Reuters) - Cable channel HBO urged critics of its planned slavery-themed drama Confederate to reserve judgment until the show develops further, in response to an intense social media campaign demanding that the project be axed.

The hashtag #NoConfederate was a top-trending Twitter topic worldwide on Sunday after Ms April Reign, who was behind the #OscarsSoWhite campaign two years ago, urged people to send a message to HBO objecting to the show.

Critics of the concept have deemed it both offensive and inappropriate, especially coming from two white male creators, David Benioff and D.B. Weiss, creators of HBO's mediaeval fantasy series Game Of Thrones.

"We believe the time to speak up is now, before the show has been written or cast. Before @hbo invests too much money into #Confederate," Ms Reign tweeted, as #NoConfederate became a trending topic during Sunday night's episode of Game Of Thrones.

HBO announced last week that Confederate, in the early stages of development, would be set in an imaginary world where slavery still exists in the United States and the nation is on the brink of a third civil war.

Responding to the backlash, the Confederate creators said last week that neither they nor the show will endorse slavery.

Ms Reign's Twitter campaign, however, suggested the controversy is unlikely to go away any time soon.

"We did it!!! We trended #1 nationwide & #2 worldwide for most of the hour. THIS is the power of social media, @HBO, & we say #NoConfederate," she tweeted late on Sunday.