The evening classes I go to may be cheap, but they are not cheerful. One of the neon strip lights in my classroom has been flickering since term began. The Venetian blinds are falling apart, and the door has to be wedged shut with a brick. When the photocopier isn't working, which is usually, there are no worksheets. Last week, the teacher mocked me when I asked a question, and this week I couldn't face going so I bunked off. I am trying to learn the vocational skills I need for the job I want, and I haven't got much money to spend. So I am stuck with a hopeless teacher in a dreary classroom at a forlorn further education college. But I am lucky. I have already had a good education from my state schools and university. Many of the people who go to the college have not.

The further education sector, a hotchpotch of public, private and charitable institutions, is supposed to mop up around the edges of schools and universities. It is responsible for the amorphous task of teaching adults everything that they do not learn elsewhere. It must teach reading and writing to prisoners, shorthand to would-be journalists, computing to middle-aged women and carpentry to 16-year-old school-leavers. Unfortunately, the availability, price and quality of private and charitable further education vary, and the public courses are a long-standing joke. There have been endless attempts to rejuvenate the sector from the Education Act 1944 onwards. But little has changed since 1975, when Trevor Griffiths's play Comedians dramatised the boredom and frustration of going to evening classes.

There is an undisputed need for further education in the UK. An estimated seven million people, a fifth of the adult population, are functionally illiterate. That means they lack the reading and writing abilities expected of the average 11-year-old. They can't fill in forms or read school reports. A survey last month by the Organisation for Economic Co-operation and Development showed that although British universities are excellent, the education given to those with the fewest qualifications is bad and, compared with the rest of Europe, getting worse. Rated according to the qualifications of those leaving secondary school, the UK is 22nd in a league table of 30 developed countries. That is down from 13th place a generation ago. There was already more a skills chasm than a skills gap, and it is getting wider.

As HSBC and train operators move their call-centres to India and Gillette threatens to shift production of its razors from Middlesex to eastern Europe, the number of low-skilled jobs available is shrinking. Even if they are literate and numerate, adults who cannot use computers, lack training in management techniques or who have no qualifications as technicians or craftsmen are becoming less and less employable. As Charles Clarke, the Education Secretary, has said, their lack of skills is bad news for themselves and bad news for Britain's economy.

Tony Blair said in 1999 that "the best defence against social exclusion is having a job, and the best way to get a job is to have a good education". A white paper titled "21st-Century Skills: realising our potential", released this summer, showed that one-third of all unemployed people in Britain have literacy and numeracy problems. Among those in prison, 80 per cent have problems with writing, 50 per cent with reading and 65 per cent with numbers.

The white paper also showed that productivity in the UK is 25 per cent lower per hour worked than in Germany and the US, and 30 per cent lower than in France. It acknowledged that this is largely because of the inadequate skills of the workforce. The Trade and Industry Secretary, Patricia Hewitt, said: "The future of the country's prosperity lies in the knowledge economy . . . We must strive to innovate, to produce high-quality, value-added products and services. And to do this, we have to ensure the right skills to support growth across all regions."

Even those who have the skills that they and the economy need today must keep learning if they are to remain employable. My mother, who trained as a midwife 25 years ago, now needs to be taught how to use spreadsheets to do her job. My aunt is less in demand as a translator from Russian than she used to be, and so is looking for a new career. My cousin who used to be a fashion designer doesn't enjoy cool-hunting now she is in her thirties, and so has retrained as a furniture restorer. All of them need, to use the government's buzzword, opportunities for lifelong learning.

But I am not the only one who has had a miserable time at a further education college. The Work Foundation, an independent think-tank, called the sector "a national disgrace" in a recent report. The authors, Alexandra Jones and Andy Westwood, describe it as "underqualified as well as under-resourced; underperforming as well as underused; under-trusted as well as mis-understood. In short . . . wholly unable to deliver what the UK requires." The Office for Standards in Education also produced a report on the government's 2001 Skills for Life strategy, which aims to boost teaching of reading, writing and arithmetic to adults. Although the strategy has enticed more people than ever back into the classroom, many of the teachers are poorly qualified, badly trained and cannot motivate their pupils, the report said.

Alexandra Jones told me that "further education is doing an amazing job, given the constraints of funding, staff and priorities". Those are serious constraints. Further education is hopelessly underfunded, especially by comparison to higher education. Universities receive £2bn of public funding per year, compared with £80m for adults in further education. University students are also entitled to interest-free loans, which the government subsidises at an estimated annual cost of £1bn and for which the rate of repayment depends on the amount the student is earning. Most adults in further education are offered only career development loans, which have to be paid back with interest over a fixed period of time, regardless of earnings. But a university degree allows graduates to earn, on average, 17 per cent more than those without higher education. Most of the people who go to my further education college are trying to learn such things as bricklaying, nursery nursing and word processing - skills that will find them jobs, but not usually jobs that attract high wages.

Andy Westwood describes the job of resuscitating the further education sector as being "like trying to turn round a huge oil tanker. It's such a big sector and the lack of resource and investment is so long-standing." The skills white paper promises more money for public further education. But the bulk of it will not come from the education budget. Part will come from students themselves, by charging higher fees to those who can afford to pay. Part will come from industry and business because, as Clarke made clear in a speech at the autumn Labour Party conference, they will benefit from a better-educated workforce. The government must perform a balancing act between increasing demand and improving supply. If I could afford to pay more for my evening classes, then I certainly wouldn't study where I am studying. As long as the quality of the teaching remains as patchy as it is at the moment, those who can afford it will go to the private institutions that reliably offer good-quality tuition.

This week while I was at a college, the fire alarm went off. Everyone filed out of the building. There were 16-year-olds in carpentry overalls, adults in lab coats, girls learning to braid hair and boys learning sound engineering. In the evening, a different crowd pours in for another lot of classes. Many of the 50 per cent of young people who the government hopes will attend university will get their entry qualifications at a further education college; some of them will earn their undergraduate degrees there. At the same time, millions of adults need to learn to read and write. All of them depend on further education. And most of them are being let down badly because Britain neglects, under-resources and ignores its public colleges.