The case for building the new Library of Birmingham on two sites has still not been properly made, a city council scrutiny committee reported today.

Committee chairman Mick Wilkes and his deputy, James Hutchings, said in a joint statement that, although some of their concerns had been addressed in a consultants' report, evidence was far from complete and there were still a number of gaps.

Backbench councillors across all parties are continuing to question the wisdom of splitting the new library - with the lending and reference centre at Centenary Square and an archive and family history centre at Millennium Point.

A decision to press ahead with the split-site solution will be taken by the council cabinet today, finally putting paid to a #179 million scheme by the architect Lord Rogers for a new library at Eastside.

The cabinet was due to take a decision following publication of an inquiry by Birmingham consultants Invigour, which concluded that only four per cent of visitors would be inconvenienced by the two-centre option.

This was because few people wanted to use resources from both the lending and reference sections and the archive and local history section during the same visit.

The claim is being disputed by the scrutiny committee, which said it was not convinced by Invigour's work.

The consultants had given insufficient weight to the fact that, at present, users have to "venture up a spiral staircase" to reach the archives on the top floor of the Central Library, making the task unappealing for borrowers.

"Greater accessibility and publicity would, we are confident, see a much greater level of usage," said Coun Wilkes (Lib Dem Hall Green) and Coun Hutchings (Con Edgbaston).

The statement added: "There is, in our view, still the need to consider the impact of taking the library out of Eastside. The risk analysis that we asked for still needs to be done.

"The Library of Birmingham may not have the sentimental attachment for citizens of Birmingham that the Town Hall has, but it is much more important in the day-to-day life of many more people.

"The emphasis on deliverability by the cabinet is understandable, but first and foremost is the need to ensure that what is delivered meets the needs of the city's objectives and requirements."