Brisbane City Council's LNP administration quietly signed its $440 million contract with Lend Lease to build its Kingsford Smith Drive upgrade last week, it was revealed in the council chamber on Tuesday afternoon.

Lord Mayor Graham Quirk had been under pressure from lord mayoral candidates Rod Harding (Labor) and Ben Pennings (Greens), along with the RACQ, not to sign any contracts prior to next year's March 19 council election.

Brisbane City Council's LNP administration quietly signed its $650 million contract with Lend Lease to build its Kingsford Smith Drive upgrade last week, Mayor Graham Quirk revealed in the council chamber on Tuesday afternoon.

But it emerged on Tuesday that that pressure was to no avail and the project, which will cost a total of $650 million, would go ahead as planned.

Cr Quirk revealed the contract had already been signed after sustained questioning by Labor opposition leader Milton Dick, who asked the Lord Mayor for project modelling prior to any signing taking place.