It has been compared to a cocktail cornichon and derided as an architectural Freudian slip, but Norman Foster’s proposed viewing platform and visitor attraction in the City of London is facing a potentially more serious objection.

Gondalas designed to move up and down the top of the Tulip tower are at risk of confusing air traffic control systems, according to technical experts at London City airport.

Construction on the 305-metre (1,000ft) tower must not go ahead until an assessment has been carried out into its potential impact on radar systems at the airport six miles to the east, officials told the authority considering whether to grant planning permission.

Foster, the architect of the neighbouring Gherkin tower as well as a £1.3bn European headquarters for Bloomberg close by, has proposed a rotating gondola ride in three-metre wide glass spheres that will take visitors on an eight-minute journey in an elliptical loop around the tower’s tip.

But London City said National Air Traffic Control must be consulted over the potential impact on radar systems, noting “the gondalas will be moving and therefore may have a slightly different effect than a static element of the building”.

The building is being developed by the Safra Group, a company controlled by the Brazilian billionaire banker Joseph Safra, which bought the neighbouring Gherkin for £726m in 2014.

The 12-storey glass bubble erected on top of a concrete stem will be filled with bars, restaurants, a viewing gallery and “a classroom in the sky”. It is more than twice the height of the London Eye, the next-tallest moving visitor attraction in the capital.

The planning application was lodged on 13 November and has already attracted some opposition from local residents.

Manuel Kaiser told City of London planners during a public consultation that “the proposal reeks of desperation in its straining after ostentatious effect”.

Anastasia Shteyn seconded Kaiser and said: “I don’t understand why we need this phallic-shaped attraction, with little aesthetic merit. As a resident of Petticoat Tower, I object to this construction project. It will create noise and turn the neighbourhood into a construction site for years to come, affecting property prices and residents’ daily comfort.”

Astrid Kirchner said it “would fit better into Dubai than London”, and Marianne Harris asked: “Is there a competition for the ugliest skyscraper?”

The Guardian’s architecture critic, Oliver Wainwright, said: “The architects may have been aiming for a tulip, but the structure is more reminiscent of a coconut shy, or an egg perched at the top of an etiolated egg cup. The structural spoons, meanwhile, have the inescapable look of obstetrical forceps, brandishing the freshly extracted Gherkin baby towards the clouds.”

Foster and Partners has been contacted for comment.