Up to a dozen traveller caravans have set up camp in Burnley's Towneley Park.
Around 12 caravans parked on a council car park close to the Todmorden Road entrance overnight on Monday, much to the annoyance of Burnley Borough Council leader Mark Townsend.
Coun. Townsend said: "This is absolutely not the right place for a group of travellers to set up camp.
"It is the last place we would want them to do that.
"It is unauthorised and illegal and absolutely unacceptable for travellers to come to a place that is meant for families, not caravans."
The police and council have been informed of the presence of the travellers.