William Hill is giving odds-on rates of 4/7 on the long-running talent show - starring a returning Simon Cowell, Amanda Holden, David Walliams and Alesha Dixon - gaining a greater audience than the BBC's big-budget import, featuring will.i.am, Sir Tom Jones, Jessie J and Danny O'Donoghue.
However, The Voice's odds aren't that low for coming out on top, at 5/4.
"The odds suggest that Britain's Got Talent will pip The Voice to the finish line, but should enough people be intrigued by the format, The Voice could get over 10 million," said William Hill spokesman Joe Crilly.
Both shows will overlap for 20 minutes between 8pm and 8.20pm on March 24, with The Voice getting a potentially important head start at 7pm.
Despite being down on its 19.2m peak in 2009, Britain's Got Talent has continued to perform well in the ratings.
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