The warning came as a coalition of business groups representing more than 6,000 firms in London urged the mayoral candidates in next May's elections to make transport their top priority.
John Prescott, the Deputy Prime Minister, has pledged to get contracts signed by next April allowing private consortia to take over responsibility for maintenance and upgrading of the Underground system, although the operation of services will remain with London Underground.
But Lord Sheppard, the chairman of London First and former chairman of Grand Metropolitan, said he shared the views of those who doubted that the public-private partnership (PPP) for the Tube would happen.
Simon Sperryn of the London Chamber of Commerce added: "Many of us are sceptical about whether the proposals the Government has made will come off."
The Government has struck a deal with Railtrack to take over the Underground's sub-surface lines and last month London Transport announced a short list of five bidders for the deep Tube lines.
But there are doubts about whether the timetable can be met. Both Lord Archer, the Conservative candidate for mayor, and Ken Livingstone who is seeking to become Labour's candidate, are opposed to the PPP.
Publishing a "Business Manifesto" for the mayoral elections, Lord Sheppard said the most important issue facing the successful candidate would be to get London's transport system working. "If you scratch most members of the business community then you find that transport is right up there as the top priority," he said. He called for public funding of pounds 200m to pounds 300m a year for transport but he said this should not necessarily be used to cut charges as Mr Livingstone did with his "fair's fair" policy in the 1980s.
"Slashing prices is not necessarily the best way of giving people what they want," said Lord Sheppard. "Customers would rather have better busses than cheaper buses."
The manifesto drawn up by London First, the Confederation of British Industry and the London Chamber of Commerce, calls on the mayoral candidates to set achievable targets in seven key areas ranging from economic development and transport to policing and the environment.
It does not contain targets itself but the chairman of the London Business Board, Michael Frye, said that if necessary business would do so and hold the mayor and the newly elected Greater London Authority to account.