Birmingham's £193 million new library will have half the space for exhibitions first envisaged, may have fewer books on offer than at present and will almost certainly be run at reduced staffing levels, it emerged last night.

Members of a city council scrutiny group set up to examine the business case for the merged library and Rep theatre in Centenary Square remained unconvinced that what was being proposed would be an improvement on the Central Library in Paradise Forum.

During a two-hour grilling of Brian Gambles, the head of library services, councillors criticised a decision to reduce exhibition space in the new library from 1,109 sq ms to 600 sq ms.

The area proposed was described by Hall Green Liberal Democrat councillor Mick Wilkes as "poky" and equivalent in size to two committee rooms in the Council House.

Mr Gambles said the specification had been reduced following a benchmarking exercise against other libraries. He accepted that the space allocated would allow less than one per cent of Birmingham's world-famous collection of Victorian photographs to be displayed, but added that a room "the size of half the city centre" would be required to show all of the stock.

Moves to reduce the number of books and journals held by the council, which began in 2005, would continue with the emphasis on discarding stock that "should not have been accepted in the first place", he added.

Mr Gambles said he had used his professional judgement to work out how much of the 30,800 sq ms in the new library would be required for books and exhibitions.

He added: "We have two million printed volumes. If we were to put them all on display the size of the library would have to be massively increased and the challenge of navigating your way around would be horrendous."

However, Coun Wilkes said the business case was full of "slippery words" designed to disguise plans to reduce the book stock.

Exact staffing levels for the new library are still under consideration, but the council's search for productivity and efficiency savings made it likely that fewer people would be employed, Mr Gambles said.

Addressing a claim by committee chairman Alistair Dow that the new library appeared to have shrunk in size since plans were first drawn up, Mr Gambles said: "There is in no respect any shrinkage of the vision. I think this has the potential to be the best public library in the world.

"I have seen no other public library that offers the scope this does. Size is only one issue."

Coun Dow (Lib Dem Selly Oak) said the council appeared to "have lost its way" on the library project.

He added: "I still have it in my head that we aren't getting the very best here. There does seem to have been a considerable reduction in space and I feel we have lost something along the way."

Ian Ward, deputy leader of the council Labour group, warned: "The difference between this proposal and previous plans for a new library is that this project is being driven by accountants rather than librarians."