Two-thirds of England's adult training centres are struggling with government literacy targets because of staff shortages, a survey says.
The government has set targets for adult education
Many depend on under-qualified, hourly paid and part-time tutors, the Times Educational Supplement reports.
An estimated seven million adults have numeracy or literacy problems.
Adult skills minister Ivan Lewis called for colleges to look for more staff following the TES's survey of 94 centres of learning.
Further education (FE) colleges, which provide the majority of adult basic skills training, are struggling hardest to run the full range of courses, the survey found.
Some 71% of FE colleges, adult and community centres and work-based learning providers reported shortages of tutors qualified to teach basic numeracy.
Literacy was close behind, with 70% reporting problems.
Around 40% of basic skills tutors are paid hourly or on part-time contracts.
Some college managers said they liked the flexibility of short contracts, but most said they had been forced on them.
Alan Tuckett, director of the National Institute of Adult Continuing Education, which carried out the survey with the TES, said: "The government's programme to improve adult basic skills has been one of its success stories - but for how long can it continue?"
The government has set a target of 1.5 million people improving their literacy, language and numeracy skills by 2007.
Mr Lewis said: "There's a cultural issue to be addressed. Probably the greatest challenge for workforce
development is to make sure we have people on the front line.
"Every college should do an audit of its staff to see which of them has these skills. It may be that there are quite a number of people who could go
into this work."
But a Department for Education and Skills spokesman branded the survey "scaremongering" and
said it "misrepresented" the progress being made.
He said: "We acknowledge that there may be staff shortages in specific areas
of the country and we are addressing this through initiatives and investment in
He added: "No questions were posed about learner achievement or targets. It is therefore nonsense to link this negative survey with the government's target to provide more adults with basic skills training."