Landscape architect Gustafson Porter has defended itself and its consultant team against accusations of poor management on the Diana Memorial Fountain in Hyde Park.
The House of Commons public accounts committee this week criticised the lack of defined roles and a "formal risk management framework" on the project, which rose from £3m to £5.2m.
But Mary Bowman, Gustafson Porter director, said the poor management was within the client group, which included the Royal Parks and Department for Culture, Media and Sport. She said: "There was top-heavy management that never delegated decisions."
Annual maintenance costs on the fountain have also doubled to £250,000, largely because of the need for additional safety measures.
After the fountain opened in July 2004, several members of the public slipped and injured themselves in its watercourse.
Bowman said: "[Safety features] were considered in the original design, but were value-engineered out because of budget pressures."
Royal Parks has acknowledged the criticism and implemented new project management systems.