British workers are spending almost £1bn a year of their own money on generative artificial intelligence tools for work, as employee adoption of the technology races ahead of corporate policies and training.

An estimated £958mn is being spent annually by workers on AI subscriptions used for their jobs, according to research from Deloitte UK involving 25,000 working adults.

The survey found 63 per cent of UK workers aged between 18 and 70 knowingly used generative AI for work. Almost half, 46 per cent, used free tools, while 34 per cent had access to externally provided AI products paid for by their employer and 17 per cent used tools developed internally.

One in six AI users paid for at least one workplace tool themselves.

The rapid adoption is creating governance challenges for employers. Almost a third of users, 31 per cent, said they used generative AI without their employer's knowledge, a practice sometimes described as "shadow AI". Almost a quarter of all UK workers said they were now using the technology daily.

Meanwhile, 65 per cent of AI users said their organisation lacked convincing leadership on how the technology should be used.

"The challenge is no longer getting people to use GenAI, it's how businesses meet this growing demand in a way that is secure, responsible and creates lasting value," said Hayley McKelvey, chief AI officer at Deloitte UK.

Workers reported saving an average of 70 minutes a week through generative AI, with most saying the additional time was used to perform more work for the same employer.

However, adoption is also generating workplace anxiety. Almost a quarter of respondents believed there was a stigma attached to using AI, while 64 per cent of weekly users worried that managers could conclude the technology was capable of doing their jobs.

Despite widespread adoption, usage remains concentrated on relatively straightforward tasks. Searching for information and drafting emails were each cited by 43 per cent of AI users, followed by creating summaries at 31 per cent.

About half of employees using generative AI at work said they had received no formal training on using it safely and effectively.

Paul Lee, head of industry insight at Deloitte UK, said employees were adopting the technology despite "limited training, patchy guidance and, in some cases, without their employer's knowledge".

He added that companies seeking greater returns would need to move beyond simply giving employees access to AI and provide clearer guardrails for how it should be used.