Enforcement teams have raided 11 hotels in the South Shore area of Blackpool as part of a crackdown on rogue operators.
Housing and planning enforcement officers from the council along with representatives of the police, fire service and Home Office took part in the joint investigation.
Businesses were visited on Wednesday following information handed to the council.
It is thought some of the properties were believed to have been illegally trading as houses of multiple occupation (HMOs).
Entry warrants were obtained in order to access each property.
Investigators will now examine all the evidence collected.
Coun Gillian Campbell, Deputy Leader of Blackpool Council, said: “Warrants were executed on 11 properties in South Shore early on Wednesday morning, following information made available to us regarding the use of the properties.
“This operation was carried out by Blackpool Council along with Lancashire Police, Lancashire Fire and Rescue Services and the Home Office and entry warrants were obtained in advance.
“We will now examine the evidence found and determine the next steps. If anybody has information about these properties then we would ask them to contact our housing enforcement team on 476841.
“We will not hesitate to investigate properties should we receive reports or have suspicions over use, obtaining warrants where necessary, and will pursue enforcement action should we find evidence of wrongdoing.”
Scott Williams from the Seaview Hotel on Dean Street, was one of the hoteliers visited as part of the operation.
He said: “They were checking that hotels were not HMOs, and I gave them access.
“But they insisted on going into bedrooms where children were getting dressed and I didn’t think that was right.
“They could have just checked with booking.com that this is a proper hotel.
“I understand they have a job to do as there are some hellholes out there, but something like this can kill a business.”