Politicians and tourism chiefs predicted the three bridges would become a major visitor draw with the completion of the £1.35 billion addition, which has been widely admired.
However, no plans have been drawn up for a central focus for tourists wanting to learn about the new crossing, the Forth Road Bridge and the Forth Bridge, which has become a world heritage site.
VisitScotland chief executive Malcolm Roughead has said: “The completion of this remarkable Scottish trilogy is a great opportunity for tourism.”
That followed the agency’s then chairman Mike Cantlay pledging two years ago: “We will be working to ensure tourism opportunities are grasped at every stage.”
Former first minister Alex Salmond also described the bridges as “iconic landmarks” which would “attract tourists from across the globe”.
When the new bridge opened two weeks ago, ministers announced plans for a Forth bridges tourism strategy “to tap into the three bridges as a unique setting and world-leading visitor destination”. However, this is not due to be unveiled until later this year.
Opposition parties said it had been left far too late.
Scottish Conservatives tourism spokeswoman Rachael Hamilton said: “A visitor centre or something similar ought to have been considered long before now.
“Instead of relentlessly patting themselves on the back for the Queensferry Crossing, the Nationalists should be asking themselves why they didn’t think of this before.”
Scottish Labour tourism spokesman Lewis Macdonald said: “It’s a pity the Scottish Government is still playing catch-up, with no plans in place for welcoming visitors now the bridge is open.
“Ministers should put that right as quickly as possible, to turn public interest into economic benefit.”
Edinburgh Western Liberal Democrat MSP Alex Cole-Hamilton said: “Ministers have had a decade to be ready for the international focus on Queensferry, but they have been found wanting.”
Network Rail is developing bridge climbs on the Forth Bridge, but a visitor centre and viewing platform are on hold due to lack of funding.
VisitScotland regional director Manuela Calchini said: “The potential for tourism is significant, but we must ensure any developments are well planned and thought out to ensure the infrastructure is there to create a smooth and enjoyable visitor journey, from transport to parking to toilets to signage and interpretation.”
Hugh Gillies, chair of the Forth Bridges Forum, which includes transport and heritage bodies, said it had “ambitious plans to create a high-quality experience that attracts visitors from across the world”.
A Transport Scotland spokeswoman said: “A number of options are being considered for a visitor centre to showcase this unique location.”