Leaders of Birmingham City Council have been urged to "go the extra mile" in an effort to secure all-party consensus on the best site for a new library.
The chairman of a highly critical inquiry into the move to build a £147 million library on split sites warned that the cabinet would be failing in its duty if it ignored the "difficult issues" raised in his report.
Mick Wilkes, chairman of the main scrutiny committee, said he regarded himself as a critical friend to the cabinet.
His inquiry, which accused senior councillors of opting for a split site without properly considering all other options, called for further consideration to be given to plans for a £ 180 million library at Eastside.
The scrutiny report said the case for a lending and reference library at Centenary Square and an archives and family history centre at Millennium Point had not been properly compared against alternatives.
Coun Wilkes (Lib Dem Hall Green) accused the council's leadership of basing the decision to opt for a split-site library on " sparse information".
He pointed out that the findings of the scrutiny committee were unanimously approved by all members - Conservative, Liberal Democrat and Labour.
" The membership is approaching 15 per cent of the full council so it is a good cross-section. The conclusion of the report reflects the evidence we considered.
"We got rid of party politics and considered the matter objectively," he added.
Coun Wilkes said Birmingham performed best when moving forward in consensus. Important regeneration projects including the NEC, the ICC and Brindleyplace had succeeded because they attracted all-party backing.
Addressing a cabinet meeting yesterday, Coun Wilkes said: "Given the magnitude of the library project it is important that all of us are prepared to go the extra mile to achieve consensus."