A property boom in the 1990s led to an explosion in holiday homes, hotels and resorts, especially along Spain's sunny eastern and southern coast, until the market crashed in 2008.
During the boom, coastal laws were often flouted, with some local governments turning a blind eye as new buildings cropped up in the world's second tourist destination after France.
Building along Spain's coast has increased in recent years as the Spanish economy has rebounded, said Pilar Marcos, who is in charge of biodiversity issues at the Spanish branch of Greenpeace.
"Construction is returning. If it seemed that the Costa del Sol is saturated, real estate firms are already selling 11,000 new homes in 200 projects," she told a Barcelona news conference called to present a new report on the state of Spain's coastal areas.
As a result, the amount of Spain's coastal land which has been built upon has risen from 240,000 hectares (593,000 acres) in 1988 to 530,000 hectares currently, according to the report.
"The occupation of the coast has been massive and this leaves a legacy of a saturated coast," Paloma Nuche, a Greenpeace representative in charge of coastal issues, told the news conference held on a boat docked in Barcelona.
Spain's Supreme Court has ordered that a symbol of this building excess -- the 21-story Azata del Sol complex on the Algarrobico beach in the Cabo de Gata park in Almeria -- should be torn down.
The Greenpeace report shows that 26.2 percent of the coast of the southern province of Malaga on the Costa del Sol has already been built on.
In the glitzy resort of Marbella in the heart of the Costa del Sol, over 90 percent of the first 500 metres (1,650 feet) of coastline have already been urbanised, according to Greenpeace.
Spain's Mediterranean coastline is the worst affected area. In the northeastern region of Catalonia, 26.4 percent of the coast has been built on, while in Andalucia, which includes Malaga, the figure stands at 15.4 percent, the Greenpeace report said.