If street names are an omen, you should be braced for trouble where Gun Street meets Artillery Lane. Conservationists and developers have long waged war in this part of east London, but never have both claimed victory in such a spectacularly bodged fashion as on this corner in Spitalfields, where a new-build block of student flats squats behind a retained Victorian facade, as if neither knew the other was there.

The fine frontage of what was once the Cock A Hoop tavern, with varying brick courses rising to ornamental stone scrollwork, now stands like a surreal stage set, propped on pins in front of a completely unrelated building. The carved stone windows now frame expanses of brick, while the students’ bedroom windows look directly on to the blank back of the preserved wall less than a metre away. Reduced to a decorative mask, to distract from the great bulk looming behind, the facade is left orphaned, rejected by both building and street as a redundant rind of history. It is a situation that makes the original wall look like the intruder, a piece of Disneyfied old London copied and pasted from elsewhere.

Facebook Twitter Pinterest High farce … The Victorian facade of the Cardiff Gas Light and Coke Company lies stranded at the base of the Altolusso tower in Cardiff. Photograph: Rightmove

While the development plumbs new depths of “facadism”, it is by no means alone in its disastrous marriage of old and new. Last year’s triumphant winner of the Carbuncle Cup, awarded for the ugliest building of the year, was another staggeringly misjudged student housing scheme, where a 350-room complex was built behind the teetering frontage of a 19th-century warehouse on -London’s Caledonian Road. With its grey flanks spilling out either side of the retained brick screen, it was like a whale trying to hide behind a seashell. Once again, floor heights differ and windows don’t line up, leaving the bedrooms with a grim prospect.

“It has become clear that most of these developers just have a standard building plan for their student hovels, and they’ll put it down regardless of what the existing facade is like,” says Hank Dittmar, former director of the Prince’s Foundation, who helped to judge the Carbuncle Cup. “It’s increasingly a problem, as more and more development is a cookie-cut commodified product. And with stratospheric land values, developers are trying to squeeze everything they can out of every parcel of land.” If it doesn’t quite fit, no matter – they’ll build it anyway.

Facebook Twitter Pinterest Death-mask … an apartment building looms above the portico of the old Unitarian Chapel on Stamford Street in Southwark. Photograph: Buildington

The practice of facadism emerged in the 1980s, when construction technology made it possible to retain a mere sliver of a frontage, and as the rise of the conservation movement increased pressure to preserve the historic streetscape – even if it didn’t care much for what happened beyond the surface. It can be done well, as along Regent Street, where vastly different interiors are cleverly inserted behind regular cream-cake facades. But too often, it remains a token gesture, even a -wilful two fingers up to the conservation officer, facades left butchered and awkwardly marooned, as if to say: “You made us keep it, and just see how you like it now.”

One such battle is evident in Cardiff, in a form of facadist high farce, where the rusticated stone frontage of the Victorian Gas Light and Coke Company building lies stranded at the base of a gleaming white apartment tower. It looks like a discarded husk from which the monumental shaft has sprouted, a tiny scrap of history at the bottom of the 23-storey monster.

Facebook Twitter Pinterest Orange slug … A new apartment building looms above the old bus depot in Lancaster. Photograph: Jonathan Duncan

A similar effect can be found on Stamford Street in Southwark, where the sturdy doric portico of the old Unitarian Chapel looks like it has lost its way, a bit-part from an ancient Greek epic washed up at the foot of another -oversized block of flats. Black glass balconies loom above the stately white pediment, mocking the remaining fragment of what once stood on the site, left here like a ghostly death-mask.

At Edinburgh’s Glasshouse hotel, facadism is taken to a whole new level. Rather than merely skinning the existing building, and pinning on the remains like a decorative brooch, the Victorian sandstone façade of the Lady Glenorchy Church is engulfed by a great glass shed. The majestic crenelations of the fortified tower are simply filled in, the whole thing swamped by a cheap curtain-wall glazing system.

Facebook Twitter Pinterest Iron maiden … CityBlock student housing in Lancaster punches a grid of windows through an existing street frontage. Photograph: Virtual Lancaster/ John Freeman

Lancaster also seems to be making a bid as the capital of botched heritage, with two fine facadist contenders. Less a preserved facade than a completely trampled building, the grade II-listed Kingsway bus depot has had a hundred flats foisted upon it in the form of a great orange slug, held over the original stone temple on chunky zigzag columns. Down the road, meanwhile, another student-housing scheme has taken lessons from London’s examples and brutally wedged a new accommodation block behind an existing street front. A relentless grid of windows has been punched through the old stone wall, as if the facade has been impaled on some kind of architectural iron maiden.

“It’s tokenism at its worst, treating architecture in only two dimensions,” says Clem Cecil of Save Britain’s Heritage. “Facadism was condemned as the bastard child of conservation when it first emerged, but it clearly hasn’t gone away.”

• This article was amended on 27 August 2014. An earlier version referred to the Victorian New College building, rather than the Gas Light and Coke Company building, in Cardiff.