Leach moved on to the Daily Mail as Britain's youngest "Page One" reporter, at age 18. In 1963, he immigrated to the United States and wrote for a number of publications (New York Daily News, People, Ladies Home Journal etc.) before launching GO Magazine and then was show Business Editor of The Star.

He got his TV start as a regular contributor to AM Los Angeles, with Regis Philbin & Sarah Purcell on KABC-TV. Other television work includes reporting for People Tonight, on CNN and Entertainment Tonight and helping start Good Morning Australia, as well as the Food Network. Leach was also a guest at the World Wrestling Federation's WrestleMania IV, where he read the rules for the championship tournament. In 1993, for the Fox network, Leach hosted an exposé documentary of Madonna titled "Madonna Xposed." The documentary was a biography of Madonna focusing on her career and publicity Stunts. Before the documentary aired, he gave Madonna a cell phone number; he claimed that at any point during the airing Madonna could call Leach and argue any point. Madonna never called and the documentary continued without incident. He also hosted Lifestyles spinoff Fame, Fortune and Romance, along with Future Today Show host Matt Lauer.

Since 1999, he has resided in Las Vegas. He wrote for the Las Vegas Sun and the daily VegasDeluxe.com website from 2008 through June 2016, when he was hired by Sheldon Adelson's Las Vegas Review Journal.

Leach appeared in the documentary film Maxed Out in 2006, which chronicled the rise of the credit card industry in the U.S. along with increased personal debt among working class people and criticized that industry's practices. Leach remarks, "Nobody would watch Lifestyles of the Poor and Unknown". The comment was highlighted by a review in the Baltimore Sun.

Leach hosted The Surreal Life: Fame Games on VH1 in 2007. He also served as the public address announcer for the 2010 NASCAR Sprint Cup race at Las Vegas Motor Speedway.