Employers have been urged to introduce different ways of working after research showed that almost 10% of people wanted to work fewer hours, even if it meant earning less.
A study by the TUC showed that half a million workers had their requests for a shorter working week turned down by their managers.
And of 100,000 workers questioned, 75% had no element of flexibility in their contracts.
Employees in the public sector were more likely to have a better work/life balance than those in private firms.
An extra 150,000 people were working flexi-time since the right to request to work flexibly was introduced 18 months ago, the study found.
TUC general secretary ,Brendan Barber, said: “Whatever the reason, employers should not see flexible working as a burden, but as a positive move that makes sound business sense.
“The right to request to work flexibly has unfortunately had little impact on the UK’s long hours culture.
“Though a few forward-thinking employers can see the benefit of a more intelligent organisation of workload and working hours, many bosses are not imaginative enough to meet flexible requests from employees with anything other than a firm ‘No’.”
Barber said extending the right to request to work flexibly to all workers might actually help more employers embrace a new working culture.
“Sadly, our figures suggest that the day when all employees can enjoy a decent work/life balance is still some considerable way off,” he added.