The Government's failure to explain its approach to implementing the Part-time Work Directive has led to confusion over the draft regulations.
Giving people more opportunities to work part-time is one of the two main intentions of the directive and was expected to be covered by the regulations.
But there is no mention in the document, out to consultation until next week, of what the Government intends to do to "identify and review the obstacles", as required by the directive. Obstacles could include inadequate child care and inflexible working patterns.
It concentrates solely on giving part-timers the same rights as full-timers, the directive's other main aim.
A DTI spokeswoman said part-time working will be promoted through a good practice guide, to be issued once the regulations are in place.
"Member states are free to choose the most effective way to promote part-time work. We believe encouraging best practice, not legislating, is the best way to do it," she said.
But the DTI was criticised for leaving employers in the dark.
"I had been telling everyone that promoting part-time opportunities was coming in the regulations and to prepare for a change of culture," said Noreen Sumra, legal adviser at consultancy Policy Network.
"Most of our clients feel they are already more than compliant in terms of rights, so this was going to be the big issue."
Caroline Noblett, partner in the employment department at law firm Edge Ellison, said the Government had caused confusion by claiming to embrace the directive then failing to legislate on one of the most important parts.
"Part-time rights are already protected indirectly through sex discrimination legislation. We had expected the legislation to deal with barriers to part time work. It was a surprise to find these are not even mentioned," she said.
"There is a huge pool of people who cannot work full time and we are losing them as a resource to the country because companies are not being creative or flexible enough to tap into it," she said.
By Dominique Hammond