A report by the Unemployment Unit says the compulsory accounts, seen as a touchstone policy for New Labour and also favoured by the Liberal Democrats, are beset by practical problems.
A key difficulty is the fact that the scheme could exclude a quarter of the working population, according to the report. Part-time, temporary and casual workers, making up an ever-increasing proportion of the workforce, would be unlikely to qualify.
The unemployed, people on low incomes and self-employed could also be kept out of the scheme, under which individuals would be required to contribute a weekly sum to their personal training account and have it matched by their employer.
The report, Called To Account, also highlights the substantial problems of administering an accounts system, the possible cost to employers and the unclear relationship with the benefits system.
Labour will flesh out details of its proposed policies on workplace training, including more detail on learning accounts, in a consultation paper due by the end of this month.
A Government consultation document on lifetime learning also seeks views on learning accounts, but ministers are known to be wary of the costs involved