To his relief, the council planning officer ruled that the windows would compromise Flannagan’s privacy and the plans were withdrawn.

But, five months later, Flannagan arrived home to find work had started on a bigger dormer extension. After being thwarted by council planners, the neighbour had expanded the proposals and gone ahead under permitted-development rules. These allow homeowners to extend their property without planning permission and there’s not a thing Flannagan or Leeds city council can do about it.

“Our house is now unsaleable,” says Flannagan. “The entire back of our property faces these huge windows and new staircase, and there’s not one room in our house that isn’t filled with this structure. We can’t understand why this is being allowed. Anyone with an ounce of common sense who stands in our house or garden can see this is completely wrong from a planning, legal and moral perspective.”

The Town and Country Planning General Permitted Development Order 2015 (GPDO) was designed to free homeowners and councils from expensive red tape when “uncontentious” modifications to properties are planned. The rules allow both homeowners and developers to extend accommodation by up to 75% without planning permission.

Opinions differ, however, on what counts as “uncontentious”. Single and double-storey side and rear extensions of up to eight metres in length are permitted under the order, as well as loft conversions and large outbuildings covering up to 50% of a property’s land.

Some residents have found their detached houses turned into semis by encroaching side extensions. Others have had their homes blighted by large outbuildings under their windows or, as in Flannagan’s case, looming roof extensions invading their private space. Worse, commercial buildings can be redeveloped into residential accommodation, allowing developers to bypass building regulations and quality control.

The government is proposing to relax the rules still further to stimulate housing capacity when the current order expires in May, including allowing homeowners and developers to extend upwards without planning permission.

However, critics warn that the policy has been badly drawn, allowing eyesores to blight residential areas and substandard accommodation to creep beneath the official radar. It has pitted neighbours against each other as the rules have left councils and homeowners powerless.

Back in 2014 when the draft proposals were announced, Birmingham city council urged the government to drop the “absurd” new rules. Its planning committee described permitted development as a planning disaster which had blighted suburbs with “monstrosities” and caused conflict between neighbours.

The government went ahead regardless, and since then the regulations have also forced the hand of councils to grant planning permission for unsuitable developments for fear, if they refused, that a landowner would come up with something worse under GPDO.

A year ago the court of appeal upheld a high court ruling that a council was justified in granting permission to a landowner to replace an agricultural building and bungalow with four houses, even though the plan was in conflict with the local development plan, because otherwise the landowner might develop the land piecemeal under permitted-development rules.

The plan was bitterly opposed by neighbours but the appeal court decided that, since the landowner was determined to maximise the value of the site, it would be better for the council to sanction a proposal over which it could retain some control.

The court rulings and Flannagan’s predicament show that permitted-development rights, while intended to benefit ordinary people who want to improve their homes, have given commercial developers a weapon with which to subdue councils.

After Leeds city council declared it would not permit the dormers proposed by Flannagan’s neighbour, the neighbour applied for a certificate of lawful development for an even more unsuitable plan.

The council tells the Observer it had to approve it, even though it had concerns about the impact, as the work qualified as a permitted development. A loophole in these rules means that although rear extensions have to be at least seven metres from the rear boundary, there is no restriction on rear dormers, which could be close enough for occupants to see neighbours in their homes.

Property lawyer Thomas Pertaia at DAS Law says those in Flannagan’s situation have little recourse, as permitted developers have essentially been given advance parliamentary approval over the heads of local planning authorities. “Unfortunately, there may be cases where easing of development rules results in a grave inconvenience to neighbours – as in this case,” he says.

Even more concerning is the fact that developers can exploit permitted-development rights to convert commercial buildings into homes without council oversight and without having to conform to minimum space, safety and living standards.

A report by the Royal Institute of Chartered Surveyors called the policy a “fiscal giveaway” from the state to private developers, and it has resulted in some appalling housing.

This month the Guardian reported on the creation of bedsits of just 18 sq metres, some lacking outside windows, in London. A few miles away, an office block on a six-lane carriageway has been converted into 60 rental units as small as 13 square metres. The government space standard requires newbuild homes for one person to be at least 37 square metres.

The Royal Town Planning Institute says government proposals to ease the rules still further and bypass local scrutiny to increase housing stock “fly in the face of democracy”.

Kit Malthouse, the minister of state for housing, said: “Increasing the availability of affordable housing is vital and, under permitted-development rules, 32,000 homes have been delivered in the past two years, providing flexibility, reducing bureaucracy, and helping us provide more properties that suit a range of needs … we are currently considering responses to our proposals to extend permitted-development rights, and a decision will be made in due course.”

It’s a vision that may look progressive on paper, but Flannagan and many others are paying a punitive price. “The government claimed the necessary checks and balances would be included to prevent the nightmare that my family now finds itself in, but clearly the rules are a set-up to benefit developers with total disregard for the environment and neighbouring properties,” he says.