America's Got Talent judge criticises 'toxic' show

She has now told Variety she raised concerns with producers but "felt singled out as being difficult".

NBC and AGT's producers said they took her concerns "extremely seriously", but they "had no bearing" on her exit.

Producers Syco Entertainment and Fremantle told BBC they and broadcaster NBC enlisted an external investigator to conduct more than 30 interviews to review the issues she raised.

"The investigation has shown that the concerns raised by Ms Union had no bearing on the decision not to exercise the option on her contract," a statement said.

She "hesitantly" raised the problem with producers, but was told that "effectively, nothing was going to change", according to Variety.

Cowell's spokesperson told Variety that "when he was directly informed of the smoking complaint during the first couple of days of the season, he immediately changed his behaviour and the issue was never raised again"

A statement about the producers' investigation into her comments said: "We have heard from contestants and talent alike that their experience on AGT has had a positive impact on their lives."