Plans to build a controversial £1 billion skyscraper in London could be set to go ahead – despite architects dismissing the project as “impossible”.

The development of the Pinnacle tower had been halted and a review process launched because of spiralling costs and serious concerns over the building’s feasibility.

Leading designers linked to the plans had said the distinctive “helter skelter” appearance wanted by the developers was far too complicated, requiring every single window to be a slightly different size.

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Yet despite an extensive review, no significant changes to the exterior of the tower have been made.

Pinnacle’s 63-storey development first stalled at a time when the Shard was struggling to fill its enormous office space, and property investors were shelving plans across the capital.

Architects KPF were asked to start a redesign in October 2012 – and reports suggest they have successfully cut costs without compromising on the tower’s bizarre visual flourish.

Changes have instead been made to the floor plans and interior, with retail space sacrificed in favour of more room for commercial offices and a larger atrium which could in theory fit in entrances for two major corporate tenants.

When the redesign was launched, rival developers moved in, with Make and PLP linked to the site. At the time Ken Shuttleworth, the chief executive of Make, told Building magazine: “The geometry of the Pinnacle is impossible. It makes the Swiss Re look simple.”

It is understood that the new designs could still require further planning permission, though it is yet to be sought.

If its construction goes ahead, Pinnacle will be the second-tallest skyscraper in the UK. Currently no more than a concrete “stump” at 200 Bishopsgate, it has a budget twice that of the £450 million Shard and would tower over Canary Wharf’s One Canada Square.

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Rebecca Evans, the editor of Construction News, said the market in London had changed hugely since the project stalled two years ago.

A survey conducted by Aecom found that the capital's top contractors have already booked in 70 per cent of their work for next year - up from around 35 per cent at this stage in 2011.

Ms Evans told The Independent: “It is a surprise that the plans have got the go-ahead without many changes, but I gather the main reason is that the developers didn’t want to go back with a fresh planning application.

“The City is also said to be keen on it – and the owners have already borrowed money for it so need to get a big return.

“People were dubious about the unusual floor design at first because it meant costs were higher, and there was a perception that for tenants there was less flexibility over what they could do with the space. The new plans seem to have addressed that and you can see how a possible additional entrance might accommodate tenants better.

“While what’s happening on the inside might actually be more important than what happens outside, Pinnacle’s USP was how different it looked, and if they’ve managed to retain the design they may be able to use that to their advantage – it will be an iconic building and now that the market has picked up that may attract more tenants.”

Developers Arab Investment declined to comment on the project.