The Dogs Trust spent a higher proportion of its income on marketing in 2002 than any other charity, according to figures from Nielsen Media Research and the Charities Aid Foundation.
During the year, Dogs Trust spent £3.3m on marketing, 12.3 per cent of its £26.8m income. Its marketing director Adrian Burder defended the expenditure as a way of generating revenue.
"Most of the money we spend on advertising is for fundraising," he said.
"We have grown enormously over the past years and increased our spending on advertising in response to that."
The research, into nine major charities, revealed that the highest-profile charities are not always the biggest spenders. The UK's biggest charity, Cancer Research UK, spent 5.5 per cent of its £338.8m income on marketing.
The NSPCC spent twice as much as the RSPCA (9.8 per cent and 4.2 per cent respectively) even though the two charities had similar incomes for that year.