A studio flat up for rent in north London is the tiniest apartment the agents letting it have seen. Measuring just 87 sq ft (eight square metres), it is so small that the only way to get into the wall-mounted bed is to stand on top of the fridge and climb up a ladder.

Once in, however, managing to wriggle out again without knocking your head on the ceiling would be quite a feat. There is certainly no chance of sitting up in bed, with just 60cm (less than two feet) of space between the top of the well-used single mattress and the ceiling.

But even though this "mezzanine-style sleeping area" seems best suited to a rather narrow rental market of petite Cirque du Soleil performers, lettings agent Alex Marks said it had received 50 to 60 inquiries about the property, due to its sought-after location half a mile from trendy Kentish Town in north London.

Converted into a self-contained, en-suite studio from a single room in a terraced house, it looks out on to a brick wall and is further proof – if any should be required – of the craziness of the capital's housing market: the property is listed on Rightmove.co.uk for rent at £180 a week (£780 a month).

This is a "competitive price" for the area, according to the landlord, and indeed, Zoopla.co.uk lists the average rent for a local one-bedroom flat at more than £1,400 per month.

Size matters



Of course, while this particular studio is exceptionally tiny, it is certainly not the only rental accommodation in London that could be classed as small.

But with rents in the capital rising by nearly 10% in the past year alone, there's a new twist on the familiar story of tenants struggling and landlords cashing in. The size of rental properties in the capital, it seems, is starting to shrink.

A fortnight ago, for example, a converted garage in Brixton, south London measuring just 110 sq ft (10 square metres) was being sold for £125,000 before being put up for rent at £700 a month. Similarly, last month, a shoebox of a flat in King's Cross – so small it was aptly described by one Guardian reader as a rabbit hutch – was being rented out for £170 a week.

The question is: is this legal? Doesn't a tenant have a right to a certain amount of space?

"Under the Landlord and Tenants Act 1985, any property let by a landlord on an assured shorthold tenancy must be 'habitable'," says Nyree Applegarth, a property litigation partner at Higgs & Sons law firm. "That means it must be sanitary, clean and a fit place to live – but there's no requirement about space."

What's more, landlords can defend small flats using a little known section of the Housing Act, which lays out the minimum space required. The standard is very low; its purpose is to enable councils to tackle serious overcrowding in rental accommodation.

For example, the act states that a studio flat that is 110 sq ft or more – so about the size of the Brixton flat – is enough space for two adults, as long as they are of the same gender or living together as husband and wife.

The studio flat in Kentish Town, north London, has a "mezzanine-style" sleeping area. Photograph: Rightmove

Meanwhile, a studio that's between 70 sq ft and 90 sq ft (so the size of the Kentish Town flat) is defined as enough space for a single adult. A room that's only slightly bigger (between 90 sq ft and 110 sq ft) is deemed suitable for an adult and a child under 10.

A landlord's obligations



What if a rental property meets these minimum standards for space, but the landlord is failing to let the property in a habitable state?

Stan Mason (not his real name) and his six housemates have experience of this scenario. They lived with a trench in their kitchen floor for two months after their landlord failed to cover it following repairs. They have a light switch cord in their bathroom that broke so many times that for two months they could only use their bathroom by moonlight and the shower in their downstairs bathroom gives them an electric shock if they use it. They pay their £3,000 a month rent by leaving an envelope of cash in their freezer.

The residents in the south London house, who are all working professionals, feel pressurised to put up with poor living conditions or face a rental market that has rocketed in price. "You do feel trapped and insecure as you don't know how long you can carry on living in this area," says Mason.

"More than a third of my income is taken up on one room's rent but we feel that if we complain the landlord will just turf us out and we could end up somewhere even worse that costs more."

Bobby Parikh, spokesperson for letting agency Charles Derby Estates, says: "There are several factors that should condemn a house to let, including mould growth, broken glass, fumes/gases, falling plaster, blocked drains, dangerous or decaying stairs, faulty gas or electrical installations, rats, cockroaches and other vermin infestations, or problems with rubbish or sewage."

A landlord also has a legal obligation to maintain the property properly by, for example, ensuring that the roof doesn't leak, the heating and plumbing system works and the electrical wiring is safe. Similarly, all gas appliances and installations must be checked annually and a gas safety certificate provided to tenants upon request.

Most importantly for studio-dwellers, a boiler should not be placed in a room used for sleeping unless it has an independent air supply (a fact that will be stated on the property's gas safety certificate). If you have any concerns about the gas safety of a property you are living in, you are entitled to ask the Gas Safe Register or the Health and Safety Executive to investigate.

Otherwise, "if your property is hazardous, and your landlord won't repair it, then complain to your local authority", advises Helen Barry, a lawyer at QualitySolicitors Rubin Lewis O'Brien. "They have legal powers to force a landlord to act."

Mason, who posted photos of his sorry-looking kitchen on Twitter as part of Shelter's campaign to improve housing says he did get in touch with the local council at one stage. "They made a list of the remedial works that needed doing and then never came back," he says.

Complaining effectively



Bear in mind that your landlord is not required to carry out any repairs until you report the problem. "Notice can be given to a landlord verbally or in writing, although it's preferable to issue a written notice so that there is proof that the landlord was made aware of the problem," says Glenn Nickols, director of online tenants community The Tenants Voice.

George Spencer, CEO of Rentify lettings agents, advises sending the landlord a dated letter and photographs in the post. "Doing it this way will cover you should things go to court."

The law states that if your landlord fails to respond and conduct the repairs within a "reasonable amount of time", you can pay for the work to be done yourself and then ask the landlord to pay you back. However, the definition of "a reasonable amount of time" will vary. "I've seen courts peg this at as little as 14 days," says Spencer. This is particularly likely to be true if the property is dangerous or you can demonstrate to a judge that the repair needed to be done for health reasons.

• This article was amended at 9am on 22 July 2014 to clarify that George Spencer is CEO of letting agency Rentify.