People are most likely to choose to improve their literacy
A £5bn scheme to boost the literacy and maths skills of 2.25m adults in England by 2010 is on target, a watchdog says.
Between 2001 and 2007 1.5m adults got the equivalent of a good GCSE in maths or English under the Skills for Life scheme, the National Audit Office said.
But it said not enough were workers who lacked basic maths skills because many had a "phobia" about the subject or were too ashamed to enrol on courses.
It also said too many people were still leaving school without these skills.
In England, 56% of adults have literacy skills below the level of a good GCSE while for maths the figure is 75%.
The report said the government had exceeded targets for the number of adults reaching basic literacy and numeracy standards (750,000 by 2004 and 1.5 million by 2007).
And it said ministers were on course to meet the 2010 target of improving the basic skills of 2.25 million adults.
But the watchdog said only 2% of workers who lacked basic maths skills had gained a numeracy qualification under the scheme between 2001 and 2007 and it warned ministers that their 2020 targets were at risk.
By 2020, ministers want 95% of adults to have the skills in the three Rs that they need for daily life - such as paying bills and reading train timetables.
Commons public accounts committee chairman Edward Leigh said the number of adults without a grasp of basic maths and English was "a big problem".
"The UK has a greater proportion of adults with the lowest level literacy and numeracy skills than many of its international competitors," he said.
"Given the greater scale of the problem in numeracy, it is disappointing that the department has done less well in raising numeracy standards."
NAO head Tim Burr said: "The Skills for Life strategy is making good progress in improving the skill levels of adults with poor literacy, language and numeracy skills.
"Building on this progress, the department needs to reduce regional variations in participation and in achievement levels for people with literacy or numeracy needs.
"It could also work more closely with other parts of government to encourage people to take up Skills for Life courses."
And Skills Minister David Lammy said: "As today's NAO report acknowledges, we have made excellent progress since our Skills for Life strategy was launched in 2001, with nearly 2 million adults gaining a first qualification since then. But we are not at all complacent.
"Processes are already in place to address some of the NAO's concerns. The government launched a national high-profile ad campaign, 'Get On', in March 2008 to increase demand for numeracy, with further activity planned over the summer."
The NAO report also highlighted the problem of young people leaving school without good skills in literacy and maths.
In 2006-07, 45% of pupils leaving school had not gained Level 2 maths (GCSE grades A*-C) and 40% had not gained Level 2 English.
More than 63,000 pupils left school without Level 1 or 2 maths (a GCSE grade A*-G) and almost 38,000 left without Level 1 or 2 English.
Alan Tuckett, director of the National Institute of Adult Continuing Education, said the signs were encouraging but big challenges remained.
The government needed to focus more on those with the lowest levels of achievement.