Birmingham Central Library has been deliberately run-down by the city council and the "dignity" of its entrance destroyed by advertising banners and fast food shops, according to the architect who designed the building.

John Madin launched a highly critical attack on plans to demolish the library, accusing officials of distorting the truth about the cost of modernising and extending the facility in Paradise Forum.

Council leaders propose to knock down the 1960s "brutalist" structure, which they say would cost £166 million to bring up to standard, and build a new £193 million library and cultural centre adjoining the Rep Theatre in Centenary Square.

Land occupied by the Central Library would be sold to kick-start a £1 billion redevelopment of Paradise Circus.

Mr Madin accused the council of exaggerating the cost of repairs and maintenance in order to justify demolishing the building and selling the site. He said the library had been deliberately designed with a view to future expansion and meeting the needs of the 21st century. All necessary repairs and improvements could be carried out for £30 million, he believed.

He accused council assistant director of culture, Brian Gambles, of making "false public statements" in The Birmingham Post about the library being unfit for purpose with a "low, dark entrance, a shallow and cramped floor".

Mr Madin added: "The dark entrance is due to the clerestory windows designed to light the entrance being covered by the cheap advertisements shutting out natural light and ruining the dignity of the Central Library entrance.

"Mr Gambles should see that these are removed and advise his employers that they should remove the fast food shops from the entrance to the library.

"Mr Gambles is clearly not aware that it is accepted in fine design to have a small scale entrance opening dramatically into a large open space as in many important buildings, including entrances to traditional buildings such as churches and cathedrals and to other civic buildings."

Mr Madin's comments were rejected by the council. Clive Dutton, director of planning and regeneration, said: "Every day is becoming like Groundhog Day on the library. Let's be clear -the cabinet has approved the business case and to underwrite a £193 million library which has the vision, quite simply, to be the best public library in the world.

"It is time to start talking about the future." n The search for a "globally renowned architect" to design the Centenary Square library began yesterday, when the city council launched a tendering exercise in the European Journal. Architects have until March 3 to submit bids for the project.