The costly flood barrier system being built in Venice to protect the city from high tides is causing controversy, with authorities divided between those who want to press ahead and others who oppose the project.

While public works minister Antonio di Pietro feels that the barrier system is the only viable solution, environment minister Alfonso Pecoraro Scanio and environmentalists

are concerned about the impact the barriers will have on the lagoon's delicate ecosystem. Many Venetians also feel that funds could be spent on cheaper and simpler alternatives and the city mayor is calling for a review of the project, known as "the Moses system".

The system consists of lining the bottom of the lagoon's three entrances with a series

of hollow steel gates that would be raised to hold back the sea during high tide.

Work began on the flood barrier system in 2003, after decades of debates and testing, with completion of the project set for 2012. It is estimated that the total cost of the project

will be around 3.5 billion.

Flooding has been an ongoing problem in Venice due to the ever-rising lagoon floor and sea levels. Experts believe that global warming and subsequent climate changes have augmented the problem.