The Spanish Parliament has passed a law aimed at controlling property speculators whom the government blames for spiralling house prices.
Spanish real estate prices have risen more than 150% in 10 years
Official documents will list everybody who has owned any piece of land in the five years before its development.
Senior local government officials will also have to declare their assets.
A number of local officials have been arrested recently on allegations of fraud, money laundering and corruption linked to housing projects.
In one of the biggest cases, nearly 60 people were arrested in the southern resort of Marbella, including a former mayor, several councillors, developers, art dealers and even a well-known singer.
The government hopes that reducing the number of speculators and the degree of corruption will bring down prices.
"With the instruments of this law we should put the brakes on exorbitant house prices," said Prime Minister Jose Luis Rodriguez Zapatero.
The new law also reserves 30% of future property development for social housing and allows for planning decisions taken over the past two years to be reviewed under certain circumstances.
It will come into force on 1 July, a few days after municipal and regional elections are held in Spain.