'London is growing up!" trumpets a sign in the window of the New London Architecture centre. Inside, there's a forest of sticks and stumps, blobs and lumps – just some of the novelty silhouettes due to appear on the city's skyline over the coming years. There are more than 230 such towers in the pipeline, a figure that shocked even the city's deputy mayor for business, who might be thought to know about such things.

Sprouting over every corner of the city, most are of an architectural quality that recalls the outskirts of Dubai or Shenzhen. The overall impression is of an unplanned free-for-all, a steroidal frenzy of building tall, with little attention to individual design quality, or the cumulative effect that these scattered hulks might have on the city.

The Planning Decisions Unit of the Greater London Authority, the body responsible for greenlighting these schemes, begs to differ. "It is simply not true to say these towers haven't been planned," says director Colin Wilson. "They have been very carefully planned. But we prefer to use a flexible framework, rather than a rigid masterplan. This liberty is what makes London successful."

The London Plan, the mayor's rulebook for development across the capital, supports tall buildings where they "create attractive landmarks enhancing London's character". It states that such developments "should be of the highest design quality … attractive to look at and, where appropriate, inspire, excite and delight".

So how are these rules shaping up in reality? Here, we give our verdict on 10 new towers, built and imminent, counting down to the very worst offender …

Location: Paddington Basin | Floors: 42 | Height: 140m | Architect: Robin Partington | Status: approved | Use: residential and hotel

1 Merchant Square

Already home to a motley collection of brash waterside blocks, all competing for attention with their jazzy cladding, Paddington Basin will soon be joined by Westminster's first skyscraper, in the form of this shiny blue cucumber. Designed by Robin Partington, architect of the Carbuncle Cup-winning Strata and the giant ground-scraping slug of Park House on Oxford Street, its apartments will apparently represent the "height of luxury living". Clad in a "midnight-blue ceramic rainscreen", this plump cousin of the Gherkin (in which Partington also had a hand) appears to be bursting out of its corset of "white porcelain ribs", which overshoot the penthouse skybar to form a tacky tiara on the skyline.

The GLA planners said: "An attractive form and a high-quality finish, and the impact of the building would be positive."

Location: City Road | Floors: 31 | Height: 100m | Architect: UN Studio | Status: on site | Use: Residential.

Canaletto

"Designed by genius", proclaim the billboards on City Road. "An architectural masterwork." Behind these slogans rises a concrete lift shaft that will soon service some of the most expensive penthouses in London. This is Canaletto, a tower designed by Professor Ben van Berkel of Dutch practice UN Studio, and one of the most hyped apartment buildings of recent times. With fat silvery frames wrapping around groups of floors in a vain attempt to break up the sheer bulk, it looks like a stack of hard drives or the back of a computer server – an accidental nod to the nearby Silicon Roundabout. The first of an unintended cluster, it has opened the doors for a thicket of forthcoming towers by Foster and Make, rising to more than half its height again.

The GLA planners said: "The materials used provide a homely feel to the building, reflecting its residential use as well as responding positively to the surrounding conservation areas."

Location: Canary Wharf | Floors: 35/29 | Height: 122/104m | Architect: Make & Darling Associates | Status: approved | Use: residential

Helix

Standing on top of a drive-through McDonald's like two oversized air ducts conjoined by a knotted tangle of wiring, the Helix towers will be a bizarre addition to Canary Wharf – a place increasingly choked by plans for silly silhouettes, each trying to stand out among the forest of corporate slabs. Designed by Make – no strangers to dressing up mindless buildings in novelty outfits – the two cylindrical towers will be connected at certain floors by sinuous metallic bands, supporting a series of "sky gardens" for a chosen few flats. Described by its developer, the real-estate arm of McDonald's, as "an intricate landmark project", you can't help feeling they've missed a trick: wouldn't a giant pair of golden arches be better?

The GLA planners said: "The images and elevation detail indicate a design that is unique and high quality."

Location: White City | Floors: 35 | Height: 141m | Architect: PLP | Status: approved | Use: residential

Terracotta wedge … Imperial West tower Photograph: /PLP Architects

The lumbering west-London cousin of Richard Rogers' Cheesegrater, the Imperial West will stand as an angular wedge on the skyline, a terracotta Dalek looming above the terraced streets of north Kensington. It is intended to be a "gateway" to London for those driving into town along the Westway, and a "landmark" for Imperial College's new campus at White City, announcing the presence of a "new ecosystem for research and innovation". So will it contain a thrilling world of skylabs and experiments in the clouds, scientists liberated from their windowless basements? Alas, no. It is another a silo of luxury flats, to be sold to fund the rest of the development, over which the tower will cast a long shadow. A local campaign group, Imperial Folly, says it "will be remembered for many years for destroying the western skyline for all those living in this part of London".

The GLA planners said: "[It will] provide a striking skyline feature and distinctive focal point that could contribute to local legibility."

Location: Vauxhall | Floors: 50 | Height: 181m | Architect: Broadway Malyan | Status: built | Use: residential.

Vauxhall Tower

Like a cigarette stubbed out by the Thames, the Vauxhall's lonely stump looks cast adrift, a piece of Pudong that's lost its way. It was generally agreed to be in the wrong place, sprouting slap-bang in the middle of the view from Westminster Bridge, and was refused permission. John Prescott, then a deputy PM keen to leave his own mark on the skyline, called the scheme in and gave it permission in 2005 – against strong warnings from his advisers that it "could set a precedent for the indiscriminate scattering of very tall buildings across London". How right they were. It has since opened the floodgates for second-rate totems that will soon turn this part of the river into mayor Boris Johnson's nightmare of "Dubai on Thames".

The GLA planners said: "The new tower is likely to result in an improvement in visual terms … it would be a welcome addition to the riverside and skyline."

Location: Stratford | Floors: 43 | Height: 133m | Architect: Stock Woolstencroft | Status: built | Use: residential.

Photograph: Martin Godwin for the Guardian

Like flies to a compost heap, developers swarmed to Stratford in the runup to the 2012 Olympics, each determined to build the "gateway to the Games" and cash in on the legacy gold-rush. Paying over the odds for small plots, they had to go tall to claw back profits. The result is a physical bar chart of inflated land values: steroidal towers now march down the high street, each trying to be more iconic than the next, forming a shouty gauntlet of cheap coloured cladding panels and bolt-on balconies. The Stratford Halo, at 43 storeys, is the biggest and boldest, wrapped with dubious purple pinstripes and topped with a jaunty quiff – and hosting a gaudy light show by night.

What the GLA planners said: "It has the potential to contribute towards the consolidation of a cluster of tall buildings at Stratford and the enhancement of its skyline."

Location: Elephant and Castle | Floors: 43 | Height: 147m | Architect: BFLS | Status: built | Use: residential.

Photograph: View Pictures/UIG via Getty Images

If south London had always felt a bit like Mordor to some, then that reputation was firmly cemented by the arrival of its very own Dark Tower in 2010, topped with no fewer than three Eyes of Sauron in the form of wind turbines – which have remained stationary ever since. Variously compared to a knuckleduster aggressively punching at the skies, or an electric razor waiting to give the clouds a quick trim, the Strata, with its sinisterly sculpted peak, has certainly put Elephant and Castle on the map. Dressed in a sporty livery of black and white stripes, it was the deserved winner of the Carbuncle Cup for the worst building of the year, "for services to greenwash [those three wind turbines have never moved], urban impropriety and sheer breakfast-extracting ugliness".

What the GLA planners said: "The proposal is welcome, as it will initiate the regeneration of Elephant and Castle … the scheme should provide a positive addition to the London skyline."

3. Walkie-Talkie

Location: City of London | Floors: 36 | Height: 160m | Architect: Rafael Viñoly | Status: Under construction | Use: office

Photograph: Stuart Forster/REX

Trumpeted as "the building with more up top", the Walkie-Talkie swells as it rises to pack in more office space at the upper levels, where rents can be higher, giving it the shape of a bulging pint glass. As a literal diagram of developers' greed, it provides the painful proof that form follows not function but finance. An aberration of the planning system, the building stands alone outside the planned City cluster, like the school bully expelled from the classroom, poking its unwelcome bulk into the skyline from almost every possible vista. Not content with looming aggressively above its neighbours and blocking out their light, the Walkie-Talkie has even scorched them with its own death ray – channeling the sun in its concave facade to temperatures capable of melting cars.

The GLA planners said: "The quality of the design would make a significant contribution to London's architecture and reinforce the distinctiveness that other tall schemes have contributed to the City skyline."

Location: Croydon | Floors: 55 | Height: 199m | Architect: CZWG | Status: approved | Use: residential and hotel

The Odalisk

"The days of drab grey buildings are at an end," pronounced Piers Gough when he unveiled his design for the Odalisk, a self-consciously whacky totem pole for Croydon, planned to house a four-star Intercontinental Hotel and luxury serviced apartments within in its lumpen shell. Looking as if it has suffered a severe mauling from a Rottweiler, the tower appears to have been ripped to pieces and stitched back together in the wrong way, standing as a monstrous Frankenstein concoction. A looping bronzed band swoops and swirls up and down the building, gouging out great gashes here and there, cutting slippery fissures into the facade, before flaring out in a graceless canopy above the street.

The GLA planners said: "The projecting and recessing features are strong elements that help add depth and character."

Location: Southwark | Floors: 31 | Height: 109m | Architect: SPARRC | Status: approved | Use: student accommodation

The Quill

What would a building look like if it had a fight with a gigantic porcupine, and the porcupine won? You can get some idea by looking at plans for the Quill, a great silver cliff-face of a thing that will sport a broken assortment of spines on its top. This ungainly hulk was miraculously granted permission by Southwark council's planning committee, who described it as "dynamic" and "dramatic", no doubt wooed by the architect's claims that the form was "inspired by the literary heritage" of the borough. The spines, you see, are supposed to look like the top of a feathered quill pen, of the kind local lad Shakespeare might have used. But there the cultural connection ends: this spiny monster will house high-end accommodation for 500 students, mostly international, who will be able to peek out from their luxury lair through mean, arrow-slit windows.

The GLA planners said: "A building with a unique composition, with a striking roof form and an architectural appearance of the highest order, consistent with the aspirations of the London Plan."