Spain's top criminal court said Wednesday it had sentenced 11 former executives of stamp firm Afinsa to up to 12 years in jail for their role in a vast scam that ruined thousands of savers.

The Madrid-based Audiencia Nacional also ordered six of the accused to pay 2.57 billion euros ($2.8 billion) in compensation for the losses incurred by investors -- including former Afinsa president Juan Antonio Cano, who was sentenced to 12 years and ten months in prison.

The court said the scam, which saw Afinsa sell low quality and sometimes fake stamps for highly inflated prices to more than 190,000 people in Spain and Portugal from 1998 to 2006, was "one of the biggest frauds our courts ever experienced."

The company promised to buy back people's stamps after these supposedly rose in value, which would see their clients recoup their initial investment plus interest, the court said.

But given that the reportedly rare stamps were actually of little value in the collectors market, initial investors were only paid thanks to the cashflow received by other newer customers, in a classic Ponzi scheme.

By 2006 when authorities started investigating the scam, Afinsa had accumulated 2.57 billion euros in liabilities.

According to the court, the investors were largely middle-class people, "who in many cases lost the savings they were keeping for retirement or for crisis situations."

In one case reported by the El Pais daily in May 2006, nearly half of the 2,300 inhabitants of the village of Dosbarrios, a farming community in the heart of the country, lost their savings.

Apart from Cano, who was found guilty of aggravated fraud and criminal insolvency, the other former executives received prison sentences ranging from two years and three months to 11 years.

They were also ordered to pay fines totalling more than 72 million euros.