The Industry Ministry said 57.4 million tourists visited Spain in 2008 -- 1.79 million fewer than in 2007 and the first reversal in visitor numbers since records began in 1995.
The number of Britons holidaying in Spain fell by 3 percent to 15.7 million as they looked for destinations outside the eurozone to avoid the effects of a 23 percent fall in the value of pound against the euro.
The industry is facing structural pressures beyond fluctuating exchange rates and the global economic crisis.
Spain is no longer the cheapest option for British and German holidaymakers looking for a break in the sun, with rivals such as Turkey and Egypt offering better-value breaks.
The appeal of 1980s-style package holidays, a stalwart of Spanish tourism, is also beginning to wane in the age of independent travel booked over the Internet.
In December, tourist numbers fell by 13.8 percent, from the same month a year earlier, after an 11 percent fall in November.
The tourism industry employs one in seven workers in Spain and generates about 10 percent of its gross domestic product.
The government had hoped the sector would remain a strong pillar of the economy, with Spain's biggest industry -- property and construction -- shrinking rapidly at the end of a 10-year boom.
Spain's Secretary of State for Tourism, Joan Mesquida, told a news conference it was unclear how this year would shape up, noting the deterioration seen in recent months " could signal a negative trend in 2009".
The number of German tourists, Spain's No.2 market, was stable at 10 million, but French visits fell 8.5 percent to 8.1 million.
Overall income from foreign tourism edged up 0.1 percent to 50 billion euros, compared with inflation that peaked at 5.3 percent in July and ended the year at 1.5 percent.
Spain is seeking to hold on to its No.2 position behind France by promoting activity-based vacations and breaks to culturally-rich cities in its interior.
Industry bosses say the government is failing to invest enough money in ageing 'sun and beach' destinations, which still account for about 70 percent of industry income. (Reporting by Ben Harding and Robert Hetz; Editing by Andrew Macdonald)