It is one of the jewels in the Spanish crown but, as the country tries to head off a debt bailout, part of the world-famous El Gordo – or "fat one" – Christmas lottery will soon slip into private hands.

Spain's socialist prime minister, José Luis Rodríguez Zapatero, today announced that the country's state lottery fund, which runs the El Gordo payout, will be partially privatised.

That means part of the proceeds from the world's biggest lottery payout will end up with private investors. Until now, profits from the ¤2.15bn (£1.8bn) Gordo went straight to the state.

About ¤700m of the money raised by El Gordo is held on to by the state lottery to cover costs and make a profit. The lottery also runs a range of weekly lotteries all year long, with profits going straight to the state.

Spain's economic crisis has meant that El Gordo is not being fattened up at the same pace as in bonanza years. This is the first year in recent memory that El Gordo has not got fatter. Organisers will be issuing the same number of tickets as last year.

Spaniards spent an average of ¤75 a head on El Gordo last year – down 3% on the previous year.

The payout has ushered in the Spanish Christmas season for almost two centuries since 1812.

Zapatero said up to 30% of the lottery would be privatised. Airports at Madrid and Barcelona were also set to be partially privatised as he sought to ease market worries about public finances.

Spain has been pummelled in recent weeks by investors who fear it may need a bailout like those given to Greece and Ireland.

The government will also stop paying ¤420 a month in February to people whose unemployment benefits have expired.