They cite the need to encourage democracy and to aid the South African economy as central reasons for their views.
However, a further 27 per cent would prefer to see whether democracy is established in the former apartheid republic before any funds are invested there.
The survey was carried out recently among 1,000 clients of Holden Meehan, a firm of financial advisers specialising in ethical investments.
Its results show how quickly attitudes towards South African investment are changing. Around six months ago, a poll by the ethical investment research group Eiris showed most fund managers adopting a wait-and- see attitude on South Africa.
Patrick Meehan, a partner at Holden Meehan, said: 'Most of our clients want ethical funds to back Nelson Mandela and the African National Congress. The message that socially responsible investments can change things must be getting through.'
Mr Meehan said that fund managers were already changing their responses to South African investments. One company, Merlin, has already lifted its blanket ban on the country. The Friends Provident Stewardship fund will make a decision after the elections next month.
There are now more than 30 green and ethical funds, worth about pounds 750m.
Mr Meehan said: 'Over the medium to long term, the average ethical fund has outperformed its equivalent conventional fund.'
For example, the average ethical pension fund showed annual growth of 14.2 per cent over the past five years. By comparison, an average UK equity pension rose by 13.4 per cent each year over the same period.
'We forecast continued resilience in that sector due to the tendency of ethical funds to lean towards smaller companies,' he added. 'As the economy comes out of recession, this picture should continue.'
Their position will be helped by a new range of EU and United States environmental directives, benefiting those companies already committed on 'green' questions.
Independent Guide to Ethical and Green Investment Funds (fifth issue) is available free from Holden Meehan on 0272 252874 or 071-404 6442.Reuse content