By Marc Frank in Havana

Cuba's ruling Communist party has launched an assault on "corruption and illegalities" that could lead to the expulsion of moderate members.

The campaign reflects the party's ideological retrenchment and underlines the extent to which the government has renounced its timid market-oriented reforms of the early 1990s.

Over the past two or three months members of the party's political bureau have visited local branches to tell militants they have one last chance to clean up their acts. The new focus on corruption has been accompanied by measures to strip state businesses of their limited operational autonomy and to scrap executive perks such as expense accounts.

A prominent voice in the anti-corruption effort has been Raul Castro, defence minister and apparently next in line to succeed his brother, Fidel Castro, as president, according to party cadres, who attended high-level party meetings two months ago. The meetings saw a video prepared as part of Raul Castro's anti-corruption drive.

"Raul was adamant that the revolution is threatened not just by the United States, but [by] corruption and liberal attitudes that give space for it to grow," said a mid-level party official. He quoted Raul Castro as saying: "Corruption will always be with us, but we must keep it at our ankles and never allow it to rise to our necks."

According to a partial transcript of a separate meeting, José Ramón Machado Ventura, a political bureau member, warned that Cuba was not only copying "capitalists' management technique, but [also] its methods and style".

Mr Machado, thought to be Raul Castro's righthand man, criticised "those who have copied capitalist methods so well that they have become capitalists themselves". A report read at the same meeting cited 219 of a total 593 audits last year that showed that "[serious problems] of corruption continue increasing in various sectors, including tourism".

Those who saw the Raul Castro video were not allowed to take notes or make recordings, but five people who have seen it say that Mr Castro was forthright in urging a crackdown on liberal attitudes.

"He insists that liberalism has led to a lack of respect for the party and government within tourism and other economic sectors, in turn creating space for corruption to blossom," said one party member.

In the film, Mr Castro concedes that Ibrahim Ferradaz, the former tourism minister, and two of three deputy ministers were replaced because they were too friendly with junior officials and unable to control corruption.

"We are not militarising tourism, but I would not hesitate to do so if I had to," Mr Castro reportedly said. He was referring to the appointment of an executive from the Gaviota group - the tourism company of Cuba's armed forces - as tourism minister, and of another to head Cubanacán, the largest state tourism corporation.

Western diplomats and analysts say the campaign may also reflect the start of the inevitable post-Fidel Castro battle for control of the party. They argue that Raul Castro is using the campaign to knock out competitors.

"Raul and the military have taken over tourism, the country's most important sector, and his men control basic industry and many other positions," one European ambassador said.