Shentall (C) is said to have danced with the group
Johnny Shentall, 23, was chosen from thousands of hopefuls who had travelled to London on Sunday to queue for auditions to replace Kym Marsh.
But the press and fans said the process had been a "stunt" after it emerged Shentall was engaged to former Steps singer Lisa Scott-Lee and an ex-member of chart group Boom!.
One newspaper has reported he may have previously performed onstage with Hear'Say.
Solicitors acting for the group issued a statement on Wednesday night saying the selection process had been fair.
The statement from Harbottle And Lewis reiterated denials made by the group earlier in the week after speculation over the speed of Shentall's selection.
It said the "plain facts of the matter" were:
Sarcastic
The Sun reported on Wednesday that Shentall had danced with Hear'Say at the Top of the Pops Awards last November, even though he and the group denied ever meeting before the auditions.
The Mirror branded the audition process a stitch-up and the Daily Mail was equally sceptical.
And many BBC News Online users emailed their views, saying they were unimpressed by the group's decision.
Hear'Say members Suzanne Shaw, Danny Foster, Noel Sullivan and Myleene Klass said on Tuesday that Shentall was the right man for the job.
"Johnny is an all-rounder, he has the right look, he sings well, dances well and is perfect for the role," said Shaw at a press conference.
Shentall's singing ability will be heard when Hear'Say's new single is released over the next few months, said their record company Polydor.
But he will be going straight to work with the group as they begin new recordings. He will also join them on tour in September.
Kym Marsh left the group last month amid a flurry of media speculation that she had fallen out with fellow member Myleene Klass
She was one of the original members of Hear'Say, who shot to fame last year after going through a gruelling selection process on the TV series Popstars.