The local Conservative group are claiming that costs for the refurbishment of the Milton Keynes Council offices have 'spiralled out of control' with the current total at £10.8 million but with fears it could go even higher.
The Labour-led Council have overseen the project since they took control in 2014 with the initial budget set at £3 million.
But the Conservative group claim that over the past four years, "silly mistakes" have caused costs to rapidly increase, with one example being the failure to identify the need for an air conditioning system.
The project was analysed by the Council's audit committee last month. It was reported at the meeting that "weak project management and governance was to blame".
It is claimed that Council officials also attempted to hide the report and other papers from the press and public but were overruled by members of the audit committee.
Leader of the Milton Keynes Conservative Group Cllr Alex Walker said: "Labour have their priorities all wrong. They turn their back on our plan to tackle homelessness and choose to fix potholes on the cheap at the same time as splashing over £10.8 million on a vanity project refurbishment."
"The choice at this election has become clear. Continue with a wasteful Labour Council or vote for change and bring in a Conservative leadership that will always make sure taxpayers receive value for money."
Chairman of the Audit Committee Cllr Peter Geary added: "This is the worst examples of mismanagement of taxpayers’ money I have seen in my time as chair of the audit committee. There has been silly mistakes throughout and a total lack of leadership. I have a real fear costs may continue to rise and I am also worried about the cost of future projects unless something significant changes at the Council."
Leader of Milton Keynes Council, Cllr Peter Marland, said: "“As usual this negative and misleading rubbish from the MK Conservatives. In order to save money to deliver services we are moving all our staff into one building, which was a scheme started by the last Tory administration."
"Unfortunately during the refurbishment needed to fit all staff into the Civic Offices the old air cooling system was condemned and needed replacing. This would have been needed anyway and calls into question why such basic costs were not established by the Tories when they signed off the scheme."
"This is yet another negative story from the local Tories. It shows they’ve got nothing at all to say about the future of our city, no positive polices, and they are incapable of even the most basic honesty in their campaign. I’d put a bet on that the people of Milton Keynes are sick of hearing this tit for tat rubbish, but sadly it’s the reality of the nasty party they are becoming in MK under their new leadership."