The ASA said the language used in the ads was "absolute" and "reinforced the implication that those who begged would use donations to fund harmful activities".
The ASA said it understood that aggressive begging was an increasing concern within Nottingham city centre and the objective of the ads was to encourage the public to give to charities.
But it added: "We further considered the ads reinforced negative stereotypes of a group of individuals, most of whom were likely to be considered as vulnerable, who faced a multitude of issues and required specialist support."
It ruled that the ads must not appear in their current forms again, adding: "We told Nottingham City Council to ensure that future ads did not portray those who begged in a manner that was likely to cause widespread or serious offence."