When Boris Johnson inaugurated The Shard, the Mayor hailed Britain’s tallest skyscraper as “a symbol of how London is powering its way out of the global recession”.

But The Shard has yet to secure its first tenant whilst six other landmark additions to London’s skyline may now never be built, developers have warned, as a mania for ever-taller buildings comes crashing to earth.

A sluggish property investment market has brought plans to build six ambitious new testaments to the capital’s supposed economic self-confidence juddering to a halt.

Construction of 100 Bishopsgate, a 172 metre skyscraper, planned to be the tallest in the City of London, is among those which have been postponed or cancelled, a BBC investigation found. A lack of advance tenants has frustrated the builders.

The £1 billion Pinnacle - nicknamed the Helter Skelter – would have been the second tallest skyscraper in the UK, towering over Canary Wharf’s One Canada Square.

Although construction began in 2009, the work has been repeatedly delayed with no completion date currently in sight. A 10-storey concrete pillar, nicknamed “the Stump”, may be its only legacy.

Plans for a “futuristic office block” called One Trinity have also been quashed and the existing building will now become a hotel.

The Can of Ham, so-called because of its distinctive shape situated near to the Gherkin on St Mary’s Axe, was given approval in 2008 but the building on its planned site has not been demolished yet.

The £450 million, 310 metre-high Shard did not have a single financial tenant to occupy its 600,000 sq ft of office space when it launched with a glitzy completion celebration in July. The Gherkin, by comparison, could boast that all of its floors had been leased when it opened in 2004.

Cannon Place is another new state-of-the-art office building which does not have a single tenant, although the developer said negotiations are on-going.

The £266 million Walbrook building near the Bank of England, which was completed in February 2010, has only let a sixth of its 445,000 sq ft of space.

Simon Rawlinson, a property development consultant at EC Harris, told the BBC’s Inside Out programme: “At the moment if you don’t have a tenant you don’t have a project, so you don’t bother.

“Projects have been cancelled or delayed in the past 12 months because they thought they had a pre-let and that fell away. Those projects had to be mothballed.”

Lee Polisano, a lead architect on the 63 storey Pinnacle, now subject of a legal battle between the contractor and developer, said: “It is a shame that we have a very important piece of land at this key site that’s empty.

“It is logical to understand in these economic times a building of that sort is a difficult building to make financially, so I am not surprised to see something so ambitious being stopped.”

Jerry Swain, regional secretary of the Union of Construction, Allied Trades and Technicians, said: “The Pinnacle is perhaps the biggest example of this recession. It’s like the hokey cokey for workers - they are in they are out, they’re in they’re out. It’s become farcical.”

Traditionalists will welcome a halt to the skyscraper boom. English Heritage complained that the Qatari-funded Shard disfigured a view of St Paul’s, while UNESCO said it compromised the “visual integrity” of the Tower of London, a World Heritage site.

The Shard’s developer, Irvine Sellar, predicted that the entire tower would be leased by the end of 2014. Developers are now demanding a pre-let – the guarantee of an occupier signing a lease – before they will commit to building a new skyscraper.

Heron Tower, Cheesegrater and Walkie Talkie, three landmark projects that are now open for business, have begun to secure tenants. The occupancy rate, however, is around one-third for the recent arrivals.

Peter Murray, chairman of London’s Centre for the Built Environment, remained optimistic. He said: “I’ve seen four recessions during my career - and in each one I’ve heard people say, ‘Look at all this empty office space, why do we need it?’ And after each one as the economy has improved, it has become occupied.”

Cancelled or awaiting tenants before construction can go on:

The Pinnacle

100 Bishopsgate

Principle Place

Wall Place

Can of Ham

One Trinity

Empty or mostly empty:

The Shard

The Place

Cannon Place

Walbrook Building

Heron Tower