Drivers are outraged a 590-space car park built to ease Civic's parking crisis will be off limits during Floriade.
The ACT Government plans to shut the Acton car park between 6am and 9am and reopen it after 9am free-of-charge for visitors to the garden festival.
Minister for Tourism Andrew Barr said he hoped drivers would forgo the car park during the event, which contributes more than $20 million to the ACT economy.
''While some commuters may wish to use these parking spaces after 9am, the Government would encourage Canberrans to help support the ACT's premier tourism event by parking elsewhere.''
Mr Barr said the provision of convenient car parking is an important part of the Government's determination to ensure Floriade remains a success.
''Floriade is the ACT's biggest single tourism event,'' he said.
The ACT Government is aiming to expand Floriade to half a million visitors. Last year there were 394,900.
But the success of the Floriade car park plan has been questioned, with some drivers indicating to The Canberra Times they intend to arrive after 9am to take advantage of free parking spaces despite Mr Barr's pleas.
Chairman of the Business Council David Marshall applauded the ACT Government for finding a solution to the problem.
''I'm aware there will be a number of very unhappy Canberrans, but for four weeks they can accommodate tourists,'' he said.
The parking spaces allocated to Floriade this year are still 250 fewer than were available in 2007.
Civic employee Dean Mansfield said the closure would be a big inconvenience.
The 26-year-old scoffed at suggestions he would be able to catch public transport during the period.
''I live in Queanbeyan. It costs $7 each way. So until ACTION is allowed to run to Queanbeyan I have to drive,'' he said.
Mr Mansfield said there was not enough parking in the city for workers and the closure of the Acton car park would lead to more problems.
ACT Tourism Industry Council chairman Joseph Griffiths said the Government's parking solution was flawed.
''I'm glad they have addressed the problem but you can't aim to grow an event and shrink the parking,'' he said.
Member for Brindabella Brendan Smyth labelled the parking situation in Civic ''a debacle''.
''It's not a solution, it's robbing Peter to pay Paul,'' he said.
''They opened Acton car park for workers because they mismanaged Civic so badly.
''Now they're taking it back for tourists.''
The head of Roads ACT, Tony Gill, said informal parking allowed for more cars than formal parking.
He said there were still paid parking places available throughout the city for Canberra's workers.
ACTION buses will run from Civic and stop on Commonwealth Avenue, providing easy access to Floriade.
Floriade runs from September 13 to October 12.