Trevor Pickup is the chief executive of the Society of St James, which runs its own drug-rehabilitation course elsewhere in the county and have homeless shelters in Portsmouth.
He said inspections by the CQC were both 'demanding' and 'extremely rigorous'.
The charity chief said: 'It is a demanding process. But if you're deemed "inadequate" it's appropriate that you're pulled up on it and improve.
'Being inadequate either means you're putting residents at risk or you are failing in another way.'
Inspectors from the CQC give no advance warning to sites they intend to assess.
Mr Pickup said monitors from the watchdog had recently visited one of the charity's services based in Southampton.
He added the organisation's reports were 'fair' and that those inspected had a chance to make comments on draft reports.
'Saying the CQC inspection was unfair is a bit like people in prison saying the court was biased against them,' Mr Pickup said. 'The CQC is genuinely fair in how they give their grades.
'If you're running a service and are inspected by the CQC, it should be a chance to show off all the good things you are doing.'