The local authorities in Venice have called the decision scandalous and irresponsible.

They say the city is increasingly vulnerable to flooding, because of the gradual erosion of its foundations and abnormally high tides caused by global warming.

They say that by 2050, much of Venice could be awash permanently. Earlier this century, flooding only occurred an average of five times a year.

Foundations crumbling

The city is built on more than 100 small islands, protected by a natural lagoon. Temporary raised walkways allow life to function much as normal during unusually high tides in winter.

But the frequency of these tides, which eat away at the foundations of the historic city, has increased.

The number of flood emergencies declared during the past 10 years has tripled.

Last year, floodwaters transformed St Marks Square - the lowest point in the city - into an outdoor swimming pool.

Air filled barriers

The rejected plan involved a system of floodgates which would rise automatically if Venice was threatened with flooding.

It had been opposed by ecologists who said that cutting off the city's freshwater lagoon from the Adriatic Sea would condemn it to a slow death.

Successive Italian Governments have been wary of committing themselves to the huge expenditure involved in closing off the lagoon, while at the same time leaving it open to shipping for the nearby port of Margara.