A campaign telling parents to send children to school if they have colds has prompted more than 6,500 signatures to a petition against its "aggressive, condescending and insulting" message.
Leaflets were sent in East Sussex County Council's Get a Grip drive to parents whose children missed at least three days of the current school year.
They also give advice on "being more organised" the night before school.
The council said it "won't flinch from this extremely serious issue".
The campaign features the slogan "good reasons for missing school - there are none".
The petition, set up by Ella Lewis of Seaford, calls for the council to withdraw the campaign and apologise for the "disgusting and offensive" alienation of parents, particularly those "struggling with serious illnesses, traumas and ongoing disabilities and conditions".
Mrs Lewis, 37, who has two children, received the leaflet after her six-year-old daughter had three days off for a chest infection and stomach bug. This equated to 91% attendance over the short autumn half term - below the council's 95% expectation.
She said: "These are unattainable standards. The council says it expects a doctor's note, but even if you could get a GP appointment, people are told not to go to the doctor's with a sickness bug.
"Schools also tell you not to allow your child back to school until you're 48 hours clear of a vomiting bug. In taking that direction, you fall into the 'persistence absence' threshold and are potentially reported to the council by the school. It's nonsensical.
"As parents we need to be able to validate our own child's health and suitability to be in school."
Mrs Lewis, who works in a school, said: "The council could have been more polite, engaging or creative.
"But they've just offended people who are trying to do their best every day for their children."
The leaflet sent out to parents also warns them about fines for unauthorised absences, including holidays during term time, and says children should attend school if they have a cold, headache or minor illness.
A council spokesman said the campaign was not aimed at parents of children who had genuine medical reasons for being absent, but for those who regularly have odd days off or holiday in term time.
He said: "We appreciate this campaign has been controversial.
"Missing even one day of school has an impact not just on a child's education but on the rest of the class, as it means the teacher has to spend time helping them catch up - to the detriment of other pupils. Missing days of school reduces children's chances of achieving success."