Wrexham council is targeting rogue landlords after a man let more than 20 migrant workers live in one house.
More than 20 people were living in the house in Holt, Wrexham
The Polish workers shared the three-bed semi in Holt, near Wrexham by "hot bunking" or using the beds in shifts.
Ian Fenn was fined £1,800 plus costs by Wrexham Magistrates last week after failing to tell officials how many people lived there.
Mr Fenn says he subsequently rehoused the tenants and will appeal to Crown Court against his conviction.
Mr Fenn, who owns 35 properties in total, allowed the Poles to live in his house in Dee Park, Holt, while they worked in the area.
One neighbour, who did not want to be named, said: "There was more than 20 people in there, in a three-bedroom house - you can imagine how cramped it must have been in there.
"They were also causing a problem for some people living around here because of all the noise they made.
"Something had to be done, it's not right.
"As far as we know, they are Polish, and there are still people in there, but we don't know how many."
Officials launched an investigation after complaints from neighbours, but the investigation was hindered when Mr Fenn failed to provide environmental health officers with information about how many people were living there.
He was eventually prosecuted for failing to co-operate, and was fined last Wednesday. He was also ordered to pay the council's costs.
Andy Lewis, Wrexham's chief public housing and public protection officer, warned: "The high level of fine should act as a deterrent to other landlords who are failing in their duty of care to their tenants.
"Mr Fenn owns a large number of properties and should have been well aware of his legal obligations.
"The failure to provide sufficient information meant that our environmental health officers were stopped from carrying out their duties in safeguarding the health and safety of the occupants."
He added: "Some landlords, whilst providing a valuable source of accommodation in Wrexham, need to be reminded that tenants should not be exposed to hazard."
The council said it has had a lot of success working with the Wrexham landlords' forum, sharing information on the new housing regulations.
Mr Fenn, speaking from Spain, said he had let the property to an engineering company who were accommodating three employees. He later discovered that a large number of other Polish people had moved in.
"I've done my best," said Mr Fenn. "I had to buy three properties to rehouse them".
Mr Fenn said he will appeal to the Crown Court and had been treated unfairly by Wrexham council. "They're trying to make an example of me," he said.
He insisted he had informed the council verbally that there were 22 people living in the property.
Keith Best, chief executive of the Immigration Advisory Service, said he "wasn't surprised" by reports of overcrowding.
Mr Best said that for some migrant workers in Britain, life could be "rough indeed" driving people into overcrowded accommodation. He believed a need for mutual support could
also contribute to the problem.
"They naturally gravitate to people of their own nationality," said Mr Best. He urged the UK government to look at the issue.