Nearly two-thirds of shoppers say being approached by a "chugger" puts them off donating to the charity being collected for, according to a survey.
Some 61% of people across the UK said being approached in the street by a paid fundraiser wearing branded clothing actively puts them off donating to that charity.
The survey, from not-for-profit fundraising website Virgin Money Giving, also found that people were more likely to donate if the person raising money was wearing an "embarrassing" fancy dress costume, during a fun run for example - with 66% of people saying they would feel more inclined to hand over cash.
And 43% of donors could be motivated to give their cash by a fundraising challenge.
People in Scotland and Newcastle are particularly likely to pile up change specifically to give to charity at Christmas, with nearly 20% of people surveyed in Scotland and more than 15% in Newcastle, the survey found.
Jo Barnett, executive director at Virgin Money Giving, said: "Charity-giving habits are changing and our research shows that people will actively avoid hassle on the high street and can be put off from giving altogether when confronted by a chugger."
Some 2,000 people took part in the survey.