Newton, 33, was signed in May after emerging from a month in rehab. Yesterday he quit his hosting gig to return there.Sources say he is struggling with alcohol and anxiety issues. Newton's management told Seven he was withdrawing ''on medical advice''.

A Seven spokesman said: ''Matthew had a strong commitment to the program. He has tried his utmost to make it work. He has the support of his family and close circle of friends as he works his way back to full health.''

Newton's departure is a blow for Seven, as The X Factor is a major element of the network's program schedule for the second half of the year. Newton has already filmed audition and boot camp episodes of the show.

Seven is unlikely to cut him from completed episodes. It is more likely to simply replace him when the show shifts into weekly live shows in September.When he emerged from rehab in May, Newton, the son of the television evergreen Bert Newton, told the Herald he was ''looking for a positive challenge''.

''I've learnt a lot over the last period of my life, and I'm a big believer it's about the people you surround yourself with,'' he said.It is understood Newton was in Europe filming segments for the show when it was decided he should return to Australia.