Work is scheduled to begin in June on a 183m (600ft) observation tower on Brighton seafront, which will be one of the tallest structures in the UK.
The attraction is expected to open to the public in 2009
The i360 tower has been given final government approval after planning permission was granted by the city council in October.
It will be built on the site of Brighton's ruined West Pier.
Rachel Clark, from the West Pier Trust, said: "We're really thrilled, it's such a relief."
Ms Clark added: "We always thought we'd get it [government approval], but the longer the delay went on the more it was jeopardising the project.
"We were worried that our development partners might move somewhere else."
The i360 tower was designed by Marks Barfield Architects, the creators of the London Eye.
A viewing pod will take people on a 20-minute ride up the spire, where the views from the top will reach for 25 miles to Bognor in the west and Eastbourne in the east.
The tower will be rooted in the middle of a heritage centre built at ground level on the seafront.
It will involve the demolition of the promenade end of the West Pier, which closed in 1975, and has since been badly damaged by storms and a fire.