Plymouth-based Travel Leaders Group, a $20 billion travel manager, has named Ninan Chacko as CEO.

Chacko replaces Barry Liben, who is returning to lead Tzell Travel Group, a division of Travel Leaders where he started his career in 1977. Liben will remain on the Travel Leaders board of directors, the company announced Wednesday.

Chacko comes to Travel Leaders from PR Newswire, a communications and marketing firm, where he was CEO for the past six years. Before that he was involved in the travel industry with positions at Worldspan, a reservation conglomerate created by Delta, Northwest and American Airlines and Sabre Holdings.

Under Liben, Travel Leaders has grown to 45,000 agents at retail and corporate travel agencies in the U.S., United Kingdom, Australia, Canada, Greece and Ireland. Its wholly owned, franchised and member agencies account for 30 percent of all agencies in North America.

Travel Leaders originally was the leisure travel division in the hospitality and travel portfolio of Carlson. It was sold to a management group in 2008.