Robbie Williams `not back for good`: source

Bandmate Gary Barlow hinted that plans are already in the pipeline to revert to a foursome.

Appearing on BBC Radio 2, he said, 'We didn't think we could do it as a four, that's the reason we split.

'So when we got back together in 2005 we said, 'Can we do it as a four-piece?' And then we came back and we did it. Although we're back with Rob right now, we still see our future as a four-piece band.'

Robbie's commitment has been called into question since he pulled out of a New Year's Eve gig with the band, citing personal reasons, and apparently failed to turn up for auditions for their appearance on TV hit Strictly Come Dancing late last year.

A friend of the star told the Daily Mail, 'It's fair to say Robbie's not 'back for good'.'

The group have a tour planned for later this year and spokesmen for the band insisted that Robbie would be appearing as planned.

He said, 'Robbie is very much committed to it.'

On the subject of how long Robbie sees himself staying with the group, the rep added, 'Take That and Robbie Williams have always said they are taking things one step at a time.'

A spokesman for Robbie said, 'He is fully committed to the band.'