The cost of refurbishing Chelmsford’s widely anticipated leisure centre and pool has rocketed by more than 40 per cent to more than £35 million – allegedly making it the most expensive in the country.

It is unclear whether the final bill – that had been initially forecast to cost Chelmsford taxpayers £25 million – would be even greater still once the centre opens in early 2019.

The council has said Riverside is a unique project designed to last 60 years and as a pool and leisure centre it was not comparable to other swimming pool projects in the country.

It has also said its town centre location next to a river is not a characteristic shared with facilities elsewhere.

Unexpected costs, such as those for cladding, sewer relocation and asbestos removal, as well as spending associated with improving the public realm areas has increased the budget, the council has said.

Chelmsford Lib Dem councillor Stephen Robinson said the ballooning costs made a mockery of the decision not to have a diving board at the centre where former world champion Rebecca Gallantree first learned her craft.

Cllr Robinson said: “With all building contracts you could worry about big building contracts and the costs.

“The original estimate was based some time before the council actually letting the contact – so by the time they had let the contract costs had gone up.

“The very first thing they got wrong was the filling of the outdoor swimming pool to turn it into a car park. The original figure was £80,000 and the eventual outturn was £205,000.

“It kind of indicated that if on that small part the figures were wrong they should be concerned about the rest of the project.

“It is now the most expensive leisure centre of the country.”

The authority has bragged that the public are fully supportive of the plans for a 25 metre ten-lane pool, a learner pool, 300-seat spectator area, flume, a gym studio and a crèche.

But there has been criticism that diving boards will not be included. Council bosses say they cannot justify spending the £5 million it may have cost on a facility that would be used by a small number of people.

Cllr Robinson said: “We were campaigning with the support of Rebecca Gallantree to retain the diving boards.

“We were told we can’t afford it.

“The fact they have added £10 million we feel undermines that.

“We wanted to keep the diving boards. There is a strong diving club in Chelmsford and if you wanted to train you would have to travel a lot further.”

Chelmsford cabinet member for leisure Julia Jeapes said: “It would have been additional costs on top of additional costs (to install diving boards).

“These things have also included a lot of public realm work that was not in the original costings and a lot of work to the existing facilities including the sports hall and ice rink.”

The council does have options to recoup some of the costs – including selling off land and the section of Riverside accommodating the existing pool near to Waterloo Lane car park for housing.