The Sustainable MotorExpo at Beaulieu has been postponed until spring next year.
Originally scheduled to take place next weekend, the event organisers say the show will instead be held in April 2014.
The delay means the long-awaited reveal of the Bluebird DC50 sports car will also be postponed.
The 360bhp electric sports car, due to be built in a limited run of 50 units to celebrate the anniversary of Donald Campbell's land and water speed records, was originally revealed in March this year.
Bluebird said it was aware of the situation, but declined to comment further.
In a statement, Sustainable MotorExpo organiser Eco Motorsport said: "During the final preparations for the Expo, we were notified of the postponement of one of its major attractions. We would rather move the event date, than disappoint visitors.
"Whilst the decision to postpone the weekend has been a difficult one – it is the right one".