Political and business leaders in Birmingham have vowed to fight back against the decision to move the Motor Show from the National Exhibition Centre to London.
Entrepreneurs, politicians and officials at the NEC expressed their disappointment at the news but said they were looking forward to fresh challenges.
The Society of Motor Manufactures and Traders said it could not reveal whether the decision to move the show to the ExCel Centre in London's Docklands would be reconsidered after 2006.
But the body, which represents the UK's motor industry, is understood to have assessed each of the last two shows that were staged at the NEC before making the decision to move the event.
Coun Mike Whitby (Con Harborne), leader of Birmingham City Council, said: "Obviously we are disappointed to hear this news, as we have enjoyed hosting the Motor Show and think Birmingham has been a great home for it.
" We understand the SMMT's need to test the market, but if and when they decide it's just not the same elsewhere we'll be ready to talk about welcoming them back. We're already putting together plans to make the NEC an even more attractive venue.
"In the meantime, the NEC continues to be a premier venue for shows and conferences and Birmingham continues to be the choice for enterprising businesses, and we'll keep working to ensure they all feel they made the right decision."
Sue Battle, chief executive of Birmingham Chamber of Commerce, said the 2004 show at the NEC had been "a real winner" which had generated a positive response from visitors.
She added: "It is a real blow to the NEC and to the business community in Birmingham and Solihull that the 2006 Motor Show is going to London. We regard the NEC as the natural home for this prestigious show.
"However, we are where we are. Birmingham and the NEC must be ready to respond by raising the profile of Birmingham and Solihull, and investing more in infrastructure."
Ian Brough, chief executive of the Black Country Chamber of Commerce, said: "We need to use this to galvanise everyone together because the region is the economic driver of the country. We need to learn the lessons of what has happened."
Simon Murphy, chief executive of Birmingham Forward, which represents the city's professional sector, said the decision was another blow for the city.
He said: "Andrew Morris and his team could not have done more to secure the Motor Show for the NEC.
"We are disappointed because this is a blow and we do not understand how the SMMT came to this decision."
Birmingham Labour MP Richard Burden, whose Northfield constituency contains MG Rover's Longbridge plant, said the SMMT and the NEC should have obtained support from outside agencies to ensure the event stayed in the Midlands.
He said: "I think there is a real issue about exactly what went wrong here.
"I would want to be assured that both sides did all they could to bring these negotiations to a conclusion.
"I will also be approaching the NEC about that and am surprised and disappointed that both sides, if things were getting this serious, didn't seek the assistance of anyone else."
On announcing the decision, the SMMTs chief executive, Christopher Macgowan, said: "While we understand this decision will come as a disappointment to the Midlands, the reality is ExCel presented a very strong bid while the NEC was unable to deliver a proposal that responded to market demands."