A third of businesses expect to hear back from an email sent to a potential supplier within two hours, with one in 10 wanting a response within half an hour, according to the Vodafone critical response time index.

The research estimates businesses lose an average of £18,840 a year by failing to reply to emails fast enough.

Being deprived of email for even a short time can also lead to extra stress and conflict in the workplace, the index suggests. More than a third (36%) of workers said a lack of access to email while out and about had created problems for colleagues back in the office.

Forty-two percent of all workers, 53% of HR staff and 54% of finance workers now say they need access to email while out of the office simply to do their job effectively, while 58% believe all employees will need mobile email access in the future with 12% believing that time had already come.

"This year we have seen mobile email access, more than ever before, become an essential piece of the business armoury," said Mark Bond, enterprise business unit director at Vodafone UK. "This survey clearly demonstrates that the way we approach our work is changing and businesses need to move to address that change."

The research also found that 35% of workers view not having mobile email while out and about as wasted time, which doubles for employees who spend at least two days a week out of the office,

The average time wasted across a month was four days per employee, the study found, equating to 31 hours.