A survey of 1,663 employees by online takeaway firm just-eat.co.uk found 58% of employees said they are working more unpaid hours than ever before, with 71% claiming they regularly work through lunch breaks and 44% reporting they often work late.
On average, respondents work four hours' extra unpaid work per week which, at the average national salary of £23,450, means working Brits are giving employers £1.5 billion unpaid labour per week.
Three quarters of employees said they would work longer hours if it meant keeping their job, although half of Brits are unhappy in their jobs.
Top 10 overworking towns in the UK and average hours overtime per week
1. Sheffield - 6.4 hours
2. London - 6.1 hours
3. Nottingham - 5.7 hours
4. Bristol - 5.3 hours
5. Edinburgh - 5 hours
6. Manchester - 4.9 hours
7. Slough - 4.6 hours
8. Glasgow - 4.6 hours
9. Newcastle - 4.3 hours
10. Walsall - 4.2 hours
