The £175m proposal for a garden bridge on the Thames is facing an escalating backlash from leading novelists, cultural figures and architects who have slammed the cost, location and “abysmal” design of the project.

Questions were raised over the procurement process last week after the Observer revealed new details on the key role played by Joanna Lumley in charming the London mayor, Boris Johnson, into backing her dream. Others argued that designer Thomas Heatherwick was the “wrong person” for the job.

Despite original plans for the bridge to be entirely paid for by private sponsors, the public contribution to the Absolutely Fabulous star’s dream of a corridor of green across the Thames has now risen to £60m – £30m from the chancellor, George Osborne, and another £30m from Johnson.

Among an abundance of critics, Sir John Tusa, former managing director of the City of London’s Barbican arts centre, said the bridge “sounds like a colossal vanity project for Lumley, Johnson and Osborne”. He added: “[It’s] extraordinary how large lumps of capital funds come out of Johnson’s and Osborne’s back pockets for their pet projects. Who needs it? Who wants it? Who will pay to run it? It all adds up to a misuse of power, position and influence.”

Will Self calls the bridge ‘crap’.

While the novelist Will Self admitted that there are “much worse things” than the garden bridge, he added: “It’s crap. But everything’s pretty crap … Lots of public spaces are being dismantled and privatised.

“I don’t like the bridge. Boris is being a dick over it, and silly old Joanna Lumley – what’s she going to do? March Gurkhas up and down it?”

The artist Grayson Perry tweeted: “It seems like a nice idea that is in the wrong place and for the wrong people. They should build it in Hull.”

Jonathan Meades, the film-maker and writer, said it was “game on” for the garden bridge “conditional upon Boris Johnson being buried in the concrete foundations”. He added that Heatherwick is “a sort of graphic designer. We’ve got a lot of brilliant architects. [He is the] wrong person; sweet guy, but not an architect.”

Grayson Perry: ‘build it in Hull’.

The author Iain Sinclair said the plans were “absolutely fine”as long as they were left in the catalogue of unbuilt folly. “That stretch of the river is now a kind of grandiose Vauxhall Gardens pleasure dome tourist attractor, with a ferris wheel and an Emirates Airlines chairlift at the other end, which carries very few passengers and gives you a nice fairground ride at a rather expensive price.”

Will Hurst, deputy editor of the Architects’ Journal, believes that many in the world of architecture are unhappy with the way the bridge appears to have “sidestepped the normal rules of planning and procurement”.

Zaha Hadid, the Iraqi-British architect, provided a sour endorsement of the bridge last week on BBC Newsnight. The designer of the London Aquatics Centre and Tokyo’s 2020 Olympic stadium said: “[Heatherwick] is a colleague, and I will support him. It could be nice, it may not be – I don’t know. It would block the view, if I would have any criticism. But on the other hand, Blackfriars station blocks the view. And everything you do in a major city is a risk, but I think it might be sometimes worth taking it.”

Zaha Hadid: ‘a risk worth taking?’

But Piers Gough, the architect responsible for the green bridge in the East End of London, believes the procurement process for the bridge is a “scandal in the making”.

“Philosophically, I think it’s wrong because the Thames is a sort of harsh river,” he added. “It’s not like Venice or even the Seine in Paris – it’s a very tidal, cold space in the middle of London. And to domesticate it with a garden bridge, you’re going to miss the point of the character of the Thames. It will look almost surreal – and not a good surreal.

“Architecturally, the ends of the bridge are abysmal: they are sort of hacked off. It’s not a good termination of the bridge – it’s inelegant – and the views of the ends of the bridge are particularly poor and ungraceful. It doesn’t look good. It isn’t a nice piece of work.”

A judicial review into the project will take place next week, scrutinising the fairness of the procurement process.