A Scottish leisure centre built by Rok was completed almost 50% over budget, it has emerged.

Renfrewshire council awarded Rok a £3.5m contract to build a sports hall in Paisley in 2006, but the outturn cost reached £5m after construction finished four months behind schedule.

Rok said £1.74m was needed for additional construction work after it was found that the council’s tender documents had failed to take account of the installation of lockers, handrails and railings, all of which the contractor paid for. Another £50,000 had to be spent on changes to M&E works.

External cost consultants were brought in by the council to control the project’s budget in mid-construction, although the project was understood to be on target to complete on time until late last year.

The contractor’s total claim for work was £1.74m, but the council agreed to pay £994,057. Alistair Lyon, Rok’s project manager on the development, said there was “no dispute” over the £700,000 shortfall, and that a settlement had been reached with the council.

Renfrewshire council said: “There is an investigation under way into the cost overrun on part of this project. We can't comment further while that investigation is continuing."