The government has been accused of rushing the development of new educational diplomas, and warned not to rush their roll-out.
MPs have criticised the development of new diplomas for 14 to 19-year-olds, which are designed to offer a middle ground between traditional theoretical learning and vocational schemes.
But, the education and skills committee reported today the bodies behind the new diplomas appeared confused. They said it was unclear at times who was responsible for making key decisions.
The report states: "It is far from clear those in charge of developing the different diplomas share a common understanding of the kinds of learning they will demand and the purposes they will serve."
Diplomas will be offered in some areas of England from 2008. The committee today called on the Department for Education and Skills (DfES) to treat the first year as a pilot scheme, being receptive to problems and prepared to modify the diplomas if necessary.
It is "absolutely essential" only a limited number of students take the diploma to begin with, MPs warned. Expansion to the rest of the country must be "slow and controlled".
The government wants to offer all 14 to 19-year-olds the option of a blended diploma by 2013. Initially students can choose from five broad work-related areas but this will expand to 14 by 2013.
Ministers have described their introduction as "the most important reform for generations".
Aside from practical concerns, the committee also criticised the way in which the government had pushed for diplomas.
It expressed its disappointment that the government had rejected Mike Tomlinson's recommendation of an over-arching diploma for 14-19-year-olds. The government is missing an opportunity to fully reform secondary education, the report noted.
To make diplomas a success, the committee said the government must convince people diplomas offer something new and exciting. Similarly, it needs to work harder to persuade schools, employers, universities and students of the value of diplomas.
Commenting on the committee report, a DfES spokesman said: "The diplomas will deliver essential skills and knowledge, hands-on experience and employer-based learning, to prepare young people for work or further study.
"They are a radical transformation of the choices available to young people. They are a genuinely exciting change to our education system."
Diplomas can be studied at different levels, broadly similar to five GCSEs at the bottom level and rising to the equivalent of three A levels.
All students will have to pass maths and English tests, as well as completing compulsory work experience. Half of students' time will be spent in work-related learning.
But, the committee said exam bodies have not been given enough time to develop specific curricula.