Half of Spain's recent economic growth can be attributed to immigration, a Spanish government-backed report says.
Many Romanians in Madrid work in the city's burgeoning building sector
The paper says that, as a whole, immigrants contribute more the nation's finances than they receive.
It says Spain - one of Europe's main sources of growth in recent years - still has "a lot of growth left".
Spain has been on the front line of Europe's immigration debate, granting amnesty to thousands of incomers, despite protests from other EU states.
There are estimated to be 3.7 million immigrants in Spain - about 8% of the population - mainly from South America, Eastern Europe and Morocco.
Spain has sought to stem the flow of poor African arrivals with patrols off the Canary Islands and repatriation deals with African countries.
But the report, written by the prime minister's main economic adviser, Miguel Sebastian, says immigrants have played a major role in the country's development.
It says 30% of growth in the past 10 years, and 50% in the last five, has been thanks to immigrants.
In the last quarter, the Spanish economy grew at the fastest rate for five years.
"Immigrants have contributed to the creation of some 50% of new jobs" since 2001 and contributed 23bn euros (£15.6bn) a year to the treasury, the report says.