We are working for longer than we are being paid for - and neither us or our employers are feeling any benefit.

A study has shown that the average British office worker is at their desk for as much as two-and-a-half days per month more than they are being paid for.

Research from Maxis Global Business Network showed that the average desk-bound Brit puts in more than 17 hours of unpaid work for every four-week period.

However, the study also showed that for all the extra hours productivity wasn't any higher for those putting in the extra hours as they "spread out" their workload and don't increase output.

But Brits are not the worst-off workers on the planet as employees in the United Arab Emirates put in another day on top of that, on average.

The average worker in the Emirates puts in 24 hours per month - the equivalent of 36 extra days per year - while Americans and employees in Hong Kong are putting in an extra 23 hours per month.

The study found that South African workers are the best off for putting in extra hours by putting in only - only - 14 extra hours per month.

Dr Leena Johns of Maxis said that having employees working extra hours may not be in a company's best interests.

"All organisations should look to create a nurturing and supportive environment that encourages productivity," he said.

"It is important that managers distinguish between employees simply sitting at their desks and working harder. They need to measure real productivity and output.

"A strong workplace culture can help motivate employees and deliver improved financial performance, with a measurable increase in revenue.

"Unhealthy or stressed employees are a cost in terms of decreased productivity, rapid staff turnover, increased healthcare costs and absenteeism."

UK legislation states that employees more than 48 hours per week over an average of a 17-week period, while under-18s can't work more than 40 hours per week.

Employees can sign an agreement to opt out of the 48 hour maximum week, but legislation states that no worker can be sacked or treated unfairly for doing so.