The Welsh baccalaureate will be introduced in stages starting from September 2007, it was revealed this week.
Jane Davidson, minister for education, lifelong learning and skills, said it was an "historic day for Wales", and claimed schools and colleges were waiting to sign up for the new qualification.
But she was accused of fudging the "million dollar question" of funding by teaching union the NASUWT Cymru. It called for the roll-out to be delayed until details are thrashed out.
There are also fears that English universities and employers are still snubbing the diploma through ignorance.
The minister claimed additional funding for the bac was already in place, as well as "hidden money" in the learning pathways budget for reforming the 14-19 curriculum. She has already accepted a recommendation from external evaluators that appropriate funding is in place for the roll-out.
But Geraint Davies, NASUWT Cymru policy officer, said: "We have always supported the bac but it could have huge workload implications if current funding levels are not continued."
Plaid Cymru went further by calling for it to be replaced with the international version. The government's target is have a quarter of Welsh schools and colleges signed up to the bac by 2010. Currently, 31 institutions are piloting the diploma at advanced, intermediate and foundation levels, equivalent respectively to A-levels and GCSEs at grades A*-C and D-G.
Brian Lightman, head of pilot St Cyres school in Penarth, Vale of Glamorgan, said the success of the bac there was down to staffing - made possible by good funding.
Speaking this week to the Welsh Assembly's education, lifelong learning and skills committee, he said training of staff was vital to win over the more sceptical.
"Pupils had too much time on their hands before and I'm glad the qualification is demanding," he added.
The bac has been piloted since 2003, first for post-16s at advanced level and, since last month, for 14-year-olds and at foundation level.
Students study conventional vocational and academic subjects, such as A-levels and NVQs, alongside a core programme including key skills, an individual research project, community service, a language module, and study of Wales, Europe and the world.
Huw Evans OBE, principal of Coleg Llandrillo, north Wales, said it was important the bac was properly funded. He claimed employers in his area were "slowly and surely" accepting it.
Keith Davies, the bac's project director, said most of the opposition appeared to come from admissions tutors. University admissions body UCAS has awarded the diploma 120 points, equivalent to an A-grade A-level.
However, William Graham, the Welsh Conservatives education spokesman, said the qualification had yet to gain wide recognition among universities and employers.
Ms Davidson has pledged to step up marketing of the bac, review its effect on teacher and pupil workload, and track students' progress at universities and in the workplace.