London's 2012 Olympic bid team have rejected reports that the poor state of the capital's transport system could deny it the chance to host the games.
Tony Blair said the government would "do all we can"
Communications director Mike Lee said it was clear the team needed to detail the "exciting transport plans... by the government and London authorities".
The bid is one of five shortlisted by the International Olympic Committee.
But the IOC said "considerable investments" must be made to upgrade London's "obsolete" railway system.
"Urban expressways and main arterial road facilities lack the capacity to provide reasonable travel times," it added.
And claims of average bus speeds of 35mph (56km/h) "appear unrealistic".
Barbara Cassani said £17bn had been earmarked for transport
Mr Lee said on Wednesday: "There are lessons to be learned from the IOC's evaluation - but much of what they examined has moved on considerably in the work we have been doing since January.
"We are in very good shape, and we are building momentum all the way to the
vote in Singapore next July," he added.
On Tuesday, bid leader Barbara Cassani said £17bn had been earmarked for transport infrastructure.
Ms Cassani added that she was fully aware of London's shortcomings.
There are proposals for a network of new transport links to move the huge influx of spectators, competitors and officials.
These include using the Channel Tunnel rail link as a shuttle service to whisk spectators from St Pancras Station and north Kent to the Olympic zone, in Stratford, east London, as well as improving existing Tube lines and extra parking around the M25.
Organisers also say London's bid is the most "compact", with the proposed venues for 17 of the 28
sports within a 15-minute journey of the Olympic Village by public transport.
London mayor Ken Livingstone said: "The government has already planned that we will run a shuttle service from King's Cross to Stratford so you can get to the heart of London from the Olympic site in just five minutes."
The Transport Secretary, Alistair Darling, has promised to deliver "outstanding" transport for the Olympics.
And the leading executives of 82 of London's largest companies have told Mr Darling they would accept a one-off supplementary business rate to fund Crossrail link - the £10bn east-west rail line that would link Heathrow with Stratford and the Isle of Dogs.
The Prime Minister, Tony Blair, has said the government will "do all we can to bring the games back to the UK".
But Conservative mayoral candidate Steve Norris told the Evening Standard: "It's time for the government to put their money where their mouth is.
"All we have had so far are warm words from Labour ministers but no actual money."
Ealing North MP Steve Pound added: "The IOC have just passed the baton to the chancellor, and he needs to spring to the finishing line now."
Labour Association of London Government chairman told the newspaper Stratford was already served by the Jubilee and Central lines, DLR, North London line and suburban rail lines from Liverpool Street, with an international Channel Tunnel station soon to open.
But the shadow sports secretary, Julie Kirkbride, told the Times newspaper London had "many hurdles to overcome".
"Labour's record on managing major infrastructure projects has not been great, and we can't afford a repeat of the Dome or the Wembley Stadium mistakes."