Head of the National Audit Office Amyas Morse has warned civil servants not to set unrealistic expectations when planning major projects.
Morse, speaking at The Public Sector Show in London, said pressure for success often encouraged people to stray from what could actually be achieved.
He warned funding cuts would result in changes to how services were provided, while the EU referendum and devolution would put more pressure on the civil service.
“Being carried away into optimism-land is a journey many intelligent people have taken but that’s why so many projects are dogged by failure,” he said.
Morse said people took actions to comply with unrealistic plans and “those actions damage the project”. “Standing up for reality is really important,” he said.
He added it was important to think about the consequences of funding decisions and to learn from mistakes. “Be honest about how it went wrong and change it next time,” he said. “If you don’t do that you don’t have a learning culture.”
He also said skills and experience were crucial. “Bright people are trumped by bright people who know what they are doing,” he said. “[Bright people] are [also] trumped by not-so-bright people who know what they are doing.”