The X Factor finalist is said to have split up with the 18-year-old after their relationship began having troubles since he reached the Judges' Houses stage of the show.
Dance teacher Poole was seen supporting Arthur backstage at his first audition for the ITV competition.
Arthur's former bandmate Richard Doney confirmed that he broke up with Poole a few weeks ago.
"They met each other through performing. Lucie is a very good singer. Over the last few years James had a number of girlfriends, but she was very special," he told The Mirror.
A source close to Arthur added: "He really liked Lucie but when he got through to the Judges' Houses stage problems started to appear.
"It became clear it was going to be almost impossible for them to maintain a relationship with James being so busy so they decided to split up. It's a shame."
James Arthur tweeted last week that he was "newly single", and was later spotted with Take Me Out star Chanelle McCleary at a London nightclub.
Insiders alleged that Arthur and McCleary were "snogging each other's faces off" at Whisky Mist.
Arthur recently slammed Digital Spy forum users, calling them "lowlifes" and "clowns" and suggesting they "should be locked up for some of the s**t they say".
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