More than 2,000 people have signed an online petition calling for Nottingham City Council to remove posters urging people not to give to beggars.
One of them features a man smoking and urges people not to "watch your money go up in smoke".
Campaigners say the posters "demonise the vulnerable" and are unfair to the homeless.
The council has defended its stance as targeting "aggressive" begging.
The best way to help the homeless is to give through a registered charity, the authority said.
£800 a day
City council leader Jon Collins said: "Community protection and the police are continually taking action against a small number of persistent beggars who can sometimes be aggressive.
"Many of these individuals appear to be rough sleeping when they have already been provided with accommodation and use the money to feed their lifestyle.
"These professional beggars can make up to £800 a day and have in the past waved notes in front of officers."
He said the council spends over £8m annually on commissioning specialist treatment services for alcohol and drug addiction.
One of the posters has been put on the eBay online auction site and has bids of more than £3,200.
Ruth Atkinson, a student from Lenton who started the petition, said: "Exploiting stereotypes like this would not be tolerated if discrimination were focused on gender, sexuality, race or religion.
"These adverts have the very real potential to increase hostility towards people who beg.
"Many homeless people depend on the money of kind strangers to buy food and shelter, and this campaign of yours is going to make their lives so much harder," she said.
"I saw the posters and thought: 'That is completely wrong to stereotype all beggars as alcoholics,' so I thought I would start a petition to see if people agree with me."