Madrid - A planned deal for the Russian oil giant Lukoil to become the biggest shareholder of Spain's top oil company Repsol YPF could collapse over lack of financing and Spanish political opposition, media reported Tuesday.

Lukoil is interested in buying nearly 30 per cent of Repsol in a deal estimated at up to 9.8 billion euros (12.5 billion dollars).

The purchase would include a 20-per-cent stake now held by the debt-ridden construction company Sacyr Vallehermoso and part of a
12.5-per-cent stake owned by Criteria, a holding of La Caixa bank.

Lukoil was willing to assume the 5-billion-euro debt run by Sacyr to buy its stake in Repsol in 2006, but was not believed to have much more money to put into the deal, according to the daily El Pais.

La Caixa was willing to help finance the deal, but the banks which had lent to Sacyr were requesting tighter guarantees from Lukoil, the economic newspaper Expansion reported.

The eventual deal has also sparked a political storm in Spain, where the conservative opposition is accusing Prime Minister Jose Luis Rodriguez Zapatero's Socialist government of willingness to allow Russians to control the strategically important energy sector.

The Zapatero government had initially helped Sacyr to obtain financing for its entry into Repsol to keep foreign companies out of the sector, the daily El Mundo said.

Yet now, the government appeared willing to allow foreign countries to determine the amount of Spaniards' electricity or gas bills, said Dolores de Cospedal of the conservative People's Party.

The government was looking into the possibilities of a European Union company taking a stake in Repsol instead of Lukoil, and for solutions to help Sacyr, whose 18-billion-euro debt could have a destabilizing effect on the banking system, Expansion said.

Banks were due to continue talks about the possible financing of a deal with Lukoil. (dpa)