Three Rivers District Council was “ill prepared” and made “fundamental mistakes” in the William Penn Leisure Centre rebuild debacle, according to political opposition.

Ralph Sangster, leader of the district’s conservative group, spoke out against the project which led to the scheme overrunning by more than two years and £4 million.

Councillor Sangster’s comments come after the Liberal Democrat-run council’s executive met tonight to discuss the external auditors report into the William Penn fiasco.

The council commissioned accountants Grant Thornton – at a cost of £18,000 – to investigate the management and running of the redevelopment.

The investigation found that the district did not have enough staff to supervise the construction and that poor performance by the architects WS Atkins Plc and Gee Construction Ltd also played a significant factor in the project’s disastrous outcome.

Ann Shaw, council leader, said: “We decided that we didn’t have the expertise to manage it so we hired a firm for a lot of money and they clearly let us down.”

She added: “There are some very useful suggestions that we can use, particularly with the South Oxhey project.

“It’s interesting that the auditor does agree with us that the council was let down by both Atkins and Gee on matters like the changing of personnel.”

While Councillor Sangster agreed that the report was insightful, praising it as “very welcome, detailed and focused” he criticised the council’s role in the project.

He said: “The contractors and the design team were at major fault over many of the issues that were contributing to the overspend and that over run of the project, but we have got here a decision which indicates we ourselves were partly to blame for the outcome in that we were ill prepared for the project and that we made fundamental mistakes in initial stages and the subsequent problems that occurred.

“All the lessons must be learned to ensure we apply them to projects in the future.”

The redevelopment of the William Penn leisure facilities began in March 2007 and was initially expected to last 12 months and cost about £4.6 million.

The auditors highlighted there were a number of risks naturally associated with a project of this scale.

However, the report said that in the William Penn project there was an absence of “formal project management”, insufficient council staff to manage a project on such a scale, poor contractor performance and unforeseen technical difficulties.

There were also a series of delays, disputes and infighting between the council and its contractors ground project to a halt, with Grant Thornton’s report stating “each contractor blamed the other for the issues that arose”.

Last year, a settlement was agreed between the council, Atkins and Gee in which the council was paid £700,000.

Grant Thornton’s report said more stringent council oversight of the project could have prevented it failing so disastrously.

It said: “The risks on this project that became issues could arguably have been more effectively mitigated at the very start of the project if the council had completed a comprehensive risk assessment.”

Liberal Democratic councillor, Roger Seabourne, said: “I don’t think that we have shied away from the fact that the project was our responsibility. The buck stops here,” adding: “But there is no way you can foresee all of the things that can happen in this situation.”