London's highest-up and most controversial roof garden has opened its doors on the 35th floor of the Walkie Talkie skyscraper - but even City planners appear to be unimpressed with the final result.

The Sky Garden, which sits atop 20 Fenchurch Street, promised to be the capital's newest public park and was one of the reasons why the vast office block was allowed to be built on the edge of a conservation area.

It was also expected to provide the best aerial view of UK's capital city.

London's highest-up - and most controversial - roof garden has opened its doors on the 35th floor of the Walkie Talkie skyscraper

The Sky Garden, which sits atop 20 Fenchurch Street, promised to be the capital's newest public park

But City planners have admitted that the hotly-anticipated garden, which opened its doors this week, is not 'quite what it was meant to be'.

Some have said the development, with its three exclusive restaurants, isn't actually a garden at all, but 'an observation deck with a few trees'.

There has also been criticism levied at the 'public' aspect of the space, after it emerged that only paying customers would be allowed up to the garden after 6pm.

The furore will again highlight the controversy which surrounded the building of the £200m skyscraper, when developers were forced to go through a public inquiry, amid complaints the block would impede the view of St Paul's.

It will also be another blow for those who backed the building, following the episode last summer in which the concave top-shape of the building - the very feature which allowed the Sky Garden to built - caused cars and businesses to melt beneath it.

Speaking after the garden's opening, a source close to the planning department told the Guardian: 'It's still very much a live issue here. Let's say it isn't necessarily quite what it was meant to be.'

But City planners have admitted that the hotly-anticipated garden is not 'quite what it was meant to be'

Some have said the development, which has three exclusive restaurants, isn't actually a garden at all, but 'an observation deck with a few trees'

The three-storey space, designed by landscape practice Gillespies, has space for 400 diners, plus an extra 200 members of the public

Peter Rees, the City of London's former chief planner, added: 'I can't say that nothing has been compromised.

'Every building is a prototype, and things have to change as they go along. But it isn't a garden.'

The three-storey space, designed by landscape practice Gillespies, boasts a Sky Pod bar on the lower terrace, as well as the Darwin brasserie and the 'refined dining experience' of the Fenchurch grill on the top level.

In all, there's room for 400 diners, plus an extra 200 members of the public.

The criticism will again highlight the controversy which surrounded the building of the £200m skyscraper, when developers were forced to go through a public inquiry

The building was given its nickname due to its unique concave shape, which means it is top-heavy

Those who would prefer just to check out the view can book to go up the tower for a one-and-a-half hour slot. The booking must be made online, three days in advance.

But, after 6pm, only paying clientele from one of the three restaurants will be allowed up to the garden.

One critic wrote: '"Public park" may be stretching it a bit. "Observation deck with a few trees" might be a more accurate description.'

Not everyone has been impressed with the photos of the roof garden, which opened this week

Another person, responding to a photo posted online, tweeted: 'Imagine it. You've climbed to the top of the greasy pole and it's not even as good as Center Parcs.'

Last year, the 37-storey building was dubbed the Walkie Scorchie when it was found that the building was channelling the sun's rays into a concentrated beam, melting vehicles parked on Eastcheap.

A two-storey scaffolding structure covered in netting was erected as a temporary solution.