Plans to “bury” Marylebone Library’s collection in a side-street basement have come under fire from residents and political opposition.

The Grade II-listed library in Marylebone Road is set to be sold to London Business School and relocated to Luxborough Street below a housing development.

A playground will have to be bulldozed for the 19 homes and subterranean reading room. This has sparked anger among campaigners who gathered more than 800 signatures to have the play area refurbished.

Yael Saunders, heading the campaign to save the playground, said: “It’s not just the playground, but also the library at stake here and I don’t see why we as a local community should have to put up with it.

“It seems a bonkers decision to put the library on a side-street where the access is very restricted and also when most of those consulted said they would prefer the library to be placed at the Moxon Street site.”

The temporary library, housed in the basement of Council House, will close in December and council bosses expect the new library – which officials say will be 75 per cent larger – will be ready in summer 2015.

The council’s cabinet opted for the Luxborough Street site over the larger and more popular Moxon Street site – currently a car park where a farmers market operates – because it will cost at least �3.3million less.

The borough’s Labour group has accused the Conservative-led council of trading in an iconic building for what will become a “second-class service” to save money.

Labour leader Cllr Paul Dimoldenberg said: “Westminster Conservatives are short-changing Marylebone residents by burying the new library in a side-street hole in the ground, so that they can sell off the valuable Moxon Street site with no community facilities.

“This is a cynical and mean-minded proposal which devalues Westminster’s library service now and for the future.”

However, libraries boss Cllr Lee Rowley branded opponents as guilty of “cynical opportunism”.

He said: “This library will be in the heart of Marylebone, close to local amenities and it will be almost on Euston Road, only a few minutes walk from the current library. It will be much bigger with many more amenities and uses.”

Gaby Higgs, chairwoman of the St Marylebone Society, said her group would accept a new location but would prefer the library not to be underground.