Three women have been threatened with a £60 litter fine for feeding bread to ducks near an outdoor swimming pool.
The three friends, who are aged between 55 and 76, said they had been throwing bread to the birds at Hilsea Lido in Portsmouth for 15 years.
However, a council officer has warned them they will be given a fixed penalty fine if they carry on as leftover bread could be seen as litter.
Portsmouth City Council said they were concerned about rats in the area.
It is feared rats could pollute the water at the open-air pool or even spread the potentially fatal Weil's disease (leptospirosis).
A council spokeswoman said: "There have been issues of vermin in the area, rats in particular, and someone was sent out to talk to people leaving food out and the situation appears to have escalated from there.
"There was a conversation about the amount of bread being used and the amount left when the ladies departed.
"The enforcement officer then went to see them the next day and he has said to them he could issue them with a penalty notice. He has not done so."