The report said that although there were early problems with the use of construction management, the method was still a success – especially compared with its use on the £511m long-delayed British Library in Euston.
The report said the advantages of using the method at Portcullis House were that contractors were expected to bear only those risks that they could control, the design team was able to work closely with contractors on high-risk packages, and work with London Underground on the Jubilee Line extension was better co-ordinated.
Despite the endorsement, the NAO recommended major changes to future major public construction work. The changes include working out whole-life costing before approving schemes, providing better training for decision-makers in Whitehall and controlling consultants' fees.
The report found that professional fees on the project grew from £21m at 1992 prices to £40m, including inflation. Architect Michael Hopkins earned £13.1m and engineer Arup was paid £3.2m.
Other expenses included a £29m overspend on the building's structure, a loss of £9.1m owing to delays to the Jubilee Line extension and £10m in legal costs.
The report said Laing found 7500 defects in the building on completion, mostly minor, including 200 loose door handles. It also found furniture costs that included desks averaging £453 per MP, chairs £474 per MP and easy chairs costing £440, as first revealed in Building.