Salford Council said the system which devised its score under the Comprehensive Performance Assessment (CPA) is "flawed".

The authority claims it was led to believe its performance would be rated as "fair" but that its score was changed "just days" prior to publication on Thursday.

Bury, Oldham, and Trafford councils were also rated "weak" while Wigan was rated "excellent".

...at the last minute, through some kind of administrative sleight of hand, we have become rated as a "weak" authority Councillor Bill Hinds

The remaining four authorities in the Greater Manchester area - Stockport, Manchester, Tameside, Bolton and Rochdale - were rated as "fair".

The CPA investigates all aspects of councils' services and rates their effectiveness.

Salford Council Leader Bill Hinds said its score was "devastating" for the city.

He added: "Since October we have been led to believe that our rating would be 'fair'.

"All the indications we received from the inspection team told us the same thing.

'No appeal'

"But at the last minute, through some kind of administrative sleight of hand, we have become rated as a 'weak' authority."

He added: "We can't appeal against that judgement now.

"In fact we don't even know exactly why we have received this last minute judgement that skews our performance score so dramatically.

"The Audit Commission themselves say they can't tell us until after the New Year."

The council's housing strategy, which had been praised by as a strong point in the previous four years, was rated as poor by inspectors this time around.

Councillor Hinds added: "To have dropped in this way is inconceivable. I cannot believe the scoring can have changed so dramatically at the 11th hour."