The singer made it through to the penultimate stages of the BBC series last year, just missing out on the live shows.
Bill was pitched against Max Milner in one epic battle performance that saw their coach Danny O'Donoghue have to decide between them.
Sending Max through to the live shows, Danny said at the time: "[Putting them two against each other] was the stupidest thing I’ve ever done in my life.”
As Bill auditioned for BGT this week, Simon Cowell wasted no time in getting some digs in.
“I didn’t watch it – like a lot of other people," the BGT boss told Bill, adding later: “We don’t have those silly battle rounds here.”
A source told The Sun newspaper: “Simon’s dislike of The Voice was clear, but he was backed by the audience who cheered his every word.
“Bill’s a very talented singer and The Voice were obviously stupid not to see that. He wowed the judges and the audience.
“The BBC will be spitting blood if Bill wins the show and goes on to be a huge success.”
The Britain's Got Talent auditions will start on ITV later this year, with The Voice UK set to return this Spring also.
Watch Bill battle Max on The Voice UK below...