Hiring consultants for Oxfordshire County Council now costs £6.3m -- an increase of more than £1m from last financial year.
Liz Brighouse, leader of the council's Labour group, is calling for a review of the use of consultants after an analysis of fees revealed the growing bill.
In 2002/3, consultants cost the county council £5.1m, while by February of the following year, 2003/4, the total bill was £6.3m.
Consultants are being paid £600,000 over three years by the county council, city council and the South East England Development Agency for a study on how to redevelop the city's West End.
The area includes the former prison site, the Westgate shopping centre and Oxpens, where a new railway station could be located.
Mrs Brighouse said: "I am very concerned that consultants are on some occasions hired as a knee-jerk reaction without considering if there is a cheaper way of doing the same job.
"Sometimes hiring consultants can put extra pressure on our own staff because the consultants are not local and our staff have to give them a detailed briefing.
"If there are times when the council's own staff could do the job instead I want that to be fully considered."
David Robertson, executive member for transport, added: "We don't have enough staff on the ground to do the work, so we have to go for external specialists."
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