A pet rescue group is concerned for the animals welfare and chose to protest after raising their worries with the RSPCA.
Michelle Page, who runs Page's Pet Rescue, said: "The house is disgusting. He has a curtain over his door which you can see fleas jumping on.
“There’s cats in there some with cat aids, most with cat flu, a couple are blind and some pregnant, more than likely inbred.
"They need saving ASAP before they die, yet no one will help to get these poor cats out.
"We’re infuriated that nothing has been done and all we’re being told is it takes time but it’s been maybe two years now.”
A spokesman from Lincolnshire Police said: “Officers attended a property at Portland Terrace, Gainsborough, on Thursday, September 9, following reports of groups of people gathering outside.
"This is believed to relate to a number of cats being kept at the address.
“There were two separate incidents. One reported at 6.16pm and another at 8.49pm.
“No one was arrested during either incident and on both occasions, the groups left the area.
“We are working alongside the RSPCA to establish the circumstances and we would urge members of the public not to speculate while we are engaged in this process.”
A spokesman from West Lindsey District Council said: “We are aware of concerns and are currently liaising with the police. At this stage, we cannot comment any further while an investigation is underway.”
An RSPCA spokesman said: “We are aware of this incident.
"Unfortunately we are unable to discuss complaints about specific people, however we are grateful to people who report suspected animal suffering to us and we would like to reassure people we will always look into and, if necessary, investigate any complaints made to us about animal welfare.
“A lot of the time issues will be dealt with by advice and education and it is not always appropriate to publicise this information for legal reasons.”