MORE than £6million was paid out under the council's "poorly managed" system for staff travel expenses, it has emerged.
Documents obtained by the Guardian show that an average of almost £800,000 has been handed over to workers every year since 2003.
An independent review into the so-called 'grey fleet', which refers to staff who use their own vehicles on council business, found serious flaws in the authority's handling of the claims.
Some documents relating to the massive claims were also found to be missing.
The council has been heavily criticised for its expenses payouts, as details have emerged in the last few months.
But the full extent of the fleet can now be revealed. According to the internal review by the Energy Savings Trust (EST), the authority could have saved £500,000 every year by switching to the Inland Revenue's recommended mileage rates.
It added: "The ability to make savings from one part of the [budget] which could then be potentially channelled into another area should be welcomed by all parties in these difficult economic times".
The report was published in July 2010 but kept secret. The review also reveals that, during the 2009/10 financial year, more than 400 mileage claims by staff were for journeys of less than three miles.
It noted a high level of travel between offices by staff and found alternatives such as video conferencing were underused.
The damning report also said the amounts paid out were among the highest in the country, but the true extent of could not be recorded due to missing data. The authors called for urgent action to address the problem.
Critics have also urged the council to urgently introduce reforms to save further “waste”.
In March the Taxpayers' Alliance campaign manager, Charlotte Linacre, said: “The council are paying well over the odds for staff to drive in comfort, whizzing by walkers who pay their over generous mileage claims.”
Blogger 'Freewheeler', who writes on cycling in the borough, said the poorly managed system needed a complete overhaul.
He said: “The council tells residents to use their cars less, but its own officers are being financially rewarded for using their cars for very short distances which could be cycled in ten minutes.”
The Guardian is awaiting a comment from the council.