The 24-strong inspectorate reported nearly 1,500 “living units” where the code had been breached in 2008. Most cases involved apartments or houses that had been divided up into several rental units, bedsits or studio flats.

The cases involved 384 landlords and 442 separate buildings, each building containing on average just over three rental units. The year before, 757 total cases were reported in 264 buildings. But the number of inspectors has doubled, leading to more investigations.

Poverty contributes to a climate in which slum landlords can prosper. Research at the University of Antwerp estimated that 15% of people in Belgium are living below the poverty line. About 180,000 families are living in circumstances making them eligible for social housing, but the housing stock just isn’t there.

The poorest are therefore often pushed into the grasp of the slumlords, who may offer the only available rented accommodation they can afford – much of it of shocking quality, with risks to hygiene, health and safety. The majority of breaches uncovered by the Inspectorate concerned single rented rooms, where electrical faults were the main cause of problems, followed by damp and poorly maintained gas heaters, with the danger of carbon monoxide poisoning.

In most cases, the threat of a court order to repair the problems is enough to bring about an improvement, but in 44 cases last year the matter went as far as the courts.

In some cases, the Inspectorate can declare a building uninhabitable, which is supposed to act as a shock to the landlord – the tenants have to move out, and the owner has to pay a tax on the empty building as well as a “slum tax”.

If an owner sells an uninhabitable building, the new owner has two years to bring everything up to standard, with the possible grant of an extension for a further two years. In addition, the new owner will be excused the tax on empty buildings.

One house on Viaduct Dam in Antwerp was declared uninhabitable in 2004, and the owner simply bricked up the entrance and left the building to rot. The tax in itself, explains city council member Frank Hosteaux, is not enough of a disincentive. The law only steps in when landlords continue to rent the uninhabitable premises, he said. In the case of abandonment, the procedure often takes years during which nothing is done about the deteriorating building.

For those who are eventually found guilty, the fines are often minimal. One woman found guilty of renting out slum apartments that brought her an income of €26,000 a month was fined €12,500. In May last year two men who rented a slum apartment where a little girl suffocated to death as a result of a faulty gas heater were each fined €2,750 and given an 18-month suspended sentence.

There does exist a provision in the law for the city to take over a building for a period of time in order to bring it up to standard and then rent it out to recoup the costs. After that has been done, the building reverts to the original owner. But the provision – the so-called social management right – has only ever been used twice, both times in Antwerp.

The Flemish government recently published a brochure in 16 languages listing agencies where the victims of slum landlords can receive advice or legal help. The booklet lists local offices of the Housing Inspectorate, plus tenants’ associations, legal advice centres and welfare agencies in each of the region’s provinces.