Trustees of the fund revealed that they had been given a cheque for pounds 3m by one unnamed company over the weekend while pledges to the international credit card hotline were being made at the rate of 300 every hour.
Mishcon de Reya, the firm of solicitors administering the Diana, Princess of Wales, Memorial Fund, said it had received a "huge volume" of donations but a spokeswoman refused to comment on some reports that it had already topped pounds 100m.
Last week, Harrods owner Mohamed Al Fayed, the father of Dodi, Diana's friend, pledged pounds 5m towards the fund.
Kate Knightley Day of Mishcon de Reya said agreements had been drawn up with a number of large companies who would make donations later this week.
"There has been a huge volume of donations," she said.
"We have had touching gifts as small as 20p - a child's pocket money Cellotaped to a handmade card, and donations from business.
"We don't have any official figures but we should start getting them in the next week subject to difficulties such as the funds taking some time clear."
Business on the international credit card hotline - phone number 0990 66 44 22 - was busy, too, with donations averaging between pounds 10 and pounds 20.
The line is capable of accepting 3,500 callers at a time.
The two trustees of the fund, Anthony Julius, a partner at Mishcon de Reya, who used to handle Diana's affairs, and Michael Gibbins, her private secretary, are understood to have drawn up a flexible trust deed that will allow them to make donations to as wide a range of good causes as possible, not only those with which the Princess was most closely associated.
Meanwhile, Tony Blair announced yesterday that Gordon Brown, the Chancellor of the Exchequer, was to set up a government committee to choose a fitting memorial to Diana.
The small group, which may include cross-party representation as well as people from charities with which the Princess was involved, will work alongside the foundation launched by the Spencer family.
The Prime Minister said on BBC's Breakfast with Frost programme that he hoped the group would complement the fund-raising that had already started.
"I think there has to be a permanent memorial and I think the best way of doing that is a lasting covenant of her work. We will look at this very closely to see what role we can play," he said.
Mr Blair added that the very best memorial would be to build a more compassionate nation to match "the generosity of spirit that typified her".
"People want the sense that there is a legacy there that is going to be taken forward and last," he said.
"Let her legacy be compassion. Let's be a better, more compassionate Britain."
All major bank branches in Britain are accepting cash and cheques, as are all Post Offices and many building societies.
Alternatively, people can send cheques either to Kensington Palace, London W8 4PU, or to The Diana, Princess of Wales, Memorial Fund, PO Box 1, London WC1B 5HW.
Cheques to the fund should be crossed "account payee only" and made out to Diana, Princess of Wales Memorial Fund.
A website has been set up on the Internet to allow people to make credit card donations.
It can be accessed on www. natwest.com/worldpay.Reuse content