The Association of Colleges has warned that the scheme, designed to replace the widely criticised Youth Training, could be threatened if too few employers are prepared to offer training.
A bad start in the face of high expectations could end up alienating already disaffected young people still further, it says.
The traineeships are outlined in a consultation paper setting forward some of the proposals made by Sir Ron Dearing following his review of 16-19 qualifications.
Under the scheme, trainees would take national vocational qualifications at foundation or intermediate level, pick up key skills and take short courses and units of other qualifications as appropriate.
The consultation paper, Maximising Potential - New Options for Learning after 16, asks for views on how every trainee on the proposed scheme can be linked to an employer, and how the programme can be made attractive to employers.
In its response, the AOC points out that government figures show employer-funded training for 17 and 18-year-olds has declined dramatically in the past decade.
The Confederation of British Industry has reported that many employers do not see their role as training providers.
The association suggests that, if employers continue to prove reluctant to support learners, ministers should consider offering tax or national insurance incentives.
Smaller companies - known to spend least on training - would need particular financial help, the AOC says.
Under the current proposals, it was "very difficult" to see how companies operating in a harsh business climate would gain financially from taking on young and inexperienced trainees.
In a recommendation that would clearly benefit its own members, the AOC also asks ministers to consider linking each trainee to a provider institution, such as a college, instead of an individual employer.
The employer would then offer support by advising on courses, arranging times for workplace visits and providing "mentoring" opportunities for students.
Without such modifications,the AOC warns, the proposed new scheme aimed at raising the profile of youth training could backfire disastrously: "False expectations at the beginning of a new national training scheme could lead to greater numbers of disaffected young people and could harm the reputation of the scheme".