The six-week study by donor information website Intelligent Giving, published this week, alleged that only four out of 50 chuggers surveyed volunteered a solicitation statement - a legal requirement if a donor is successfully recruited.
One was said to have encouraged a prospective donor to give a false age on a direct debit form and others - two from Great Ormond Street Hospital Children's Charity - were alleged to have blocked the paths of members of the public.
A spokeswoman for the hospital charity said it was looking into the reports. "We take such allegations very seriously," she said. "We receive very few complaints - but when we do, we act upon them immediately."
Volunteering charity WRVS said it would be "looking at its training programme" after one fundraiser was said to be unable to say what the 'W' stood for in the charity's name and two others allegedly implied they were volunteers.
"Clearly they should never describe themselves as WRVS volunteers," said Paul Twocock, head of media and public affairs at the charity. It would ensure such exceptions did not happen again, he said.
The survey said that 15 of the fundraisers, including one from Scope, did not stop their pitches when asked to. The disability charity said it was investigating and would take action.
"We are glad this has been brought to our attention," said Alexandra O'Dwyer, director of communications and marketing at Scope. "This incident is very much an exception to the rule."