Google's "20 per cent time", the policy of allowing its staff a fifth of the working week to focus on a personal project, has been all but abolished, according to former employees.
The one-day-per-week allowance has been an integral aspect of the tech giant's corporate culture since its early days, and led to the creation of innovative Google products such as AdSense, Google News and Gmail.
But Silicon Valley message-boards are abuzz following a report by the website Quartz, in which former staff claimed that the majority of employees now found it impossible to take time away from their core responsibilities at the company.
Google staff reportedly refer to 20 per cent time as "120 per cent time", suggesting they can only pursue their own ideas on top of their punishing formal schedules.
Google's casual, collegial working environment has long been held up as a model for the future, and 20 per cent time was one of many employee perks intended to attract entrepreneurial workers.
Google founders Larry Page and Sergey Brin, and former chief executive Eric Schmidt, are said to have taken advantage of the policy, while other tech firms have introduced their own versions.
Twenty per cent time has always been an informal programme, rather than official company practice.
Yet when Google went public in 2004, Page and Brin wrote in an open letter: "We encourage our employees, in addition to their regular projects, to spend 20 per cent of their time working on what they think will most benefit Google.
"This empowers them to be more creative and innovative."
Google responded to the Quartz report by claiming that 20 per cent time was alive and well.
Last year, however, it emerged that staff were required to gain approval before embarking on a 20 per cent project.