Volunteer charities face a recruitment crisis as cash-strapped students spend more time working to make ends meet.
Organisations that rely heavily on students raising funds to take part in voluntary programmes overseas have seen applications drop by nearly a third this year.
Others report a boom in levels of interest but no change in the number of students who are able to follow up their enquiries with an application.
Charity leaders are predicting that participation in longer programmes, which offer students the chance to experience working in a third world country for weeks or even months, are becoming the preserve of the rich.
Kelly Drake, chief executive of the National Centre for Student Volunteering in the Community (Scadu), said there was no question that the introduction of tuition fees had had an impact on recruitment.
"Most students are having to work. They have to be very good time managers and determined if they are going to find the time to take part in an unpaid volunteer programme. It will soon be only the richer students who can afford to do it," she said.
Scadu was awarded Pounds 545,000 in National Lottery money this month to aid recruitment.
Ms Drake said there had been a marked increase in the number of students joining shorter and part-time programmes.
Many charities were having to be more flexible to help students juggle paid work, course work and volunteer work.
Health Projects Abroad, which sends students to Tanzania for three months to help build health centres or schools, has suffered a 30 per cent drop in applications this year. It is the first time the charity, which attracts mostly gap-year students and recent graduates and has been running for ten years, has experienced recruitment problems.
Simon Headington, HPA director, said: "The only explanation we can think of is that students' financial circumstances now mean there is much more pressure on them to work and get into the job market as soon as possible. It means there is less time for them to get involved in volunteer work."
Mr Headington said students who could not spare the time to take part in the programme were missing the opportunity to develop and demonstrate the kind of skills most employers were looking for.
"The students raise Pounds 3,000 to take part, which means a lot of effort and planning and being able to market what you are trying to do. The experience has often helped them find jobs at the end," he said.