Portsmouth's troubled landmark, the Spinnaker Tower, is facing more "deeply frustrating" delays, despite plans for it to open by the end of the month.
Small defects were found in the tower's concrete last year
The 170m (558ft) tower cannot open to the public because work still needs finishing on its external glass lift.
A city council spokesman said it would take up to one week before the lift had all its safety certificates.
The situation would then be reviewed to see if it could open before the Bank Holiday weekend, he said.
Council leader, Gerald Vernon-Jackson, said: "This news that further work is needed to the lift is deeply frustrating and extremely disappointing for everyone - all those many people waiting to get up the tower and all those involved in the project.
"Further delay was the last thing anyone wanted.
"The bottom line though is that we can't move until the lift has its safety certificates. Our hands are completely tied."
The Spinnaker Tower - originally planned to be completed in time for the new Millennium - is due to open to the public this summer after years of problems and spiralling costs.
Most recently, fears over the concrete used in the tower's contruction were dismissed by experts after small defects were found during a routine inspection in March 2004.
Remedial works had been carried out to correct the faults.
The tower, which was to have been entirely privately-funded, has cost taxpayers more than £10m.
Its operators missed out on potential income from thousands of visitors to the Trafalgar 200 and International Festival of the Sea events, which were both held earlier in the summer.