Former Croatian prime minister Ivo Sanader and his political party have been found guilty of rigging public tenders and abusing state funds in the biggest corruption trial to date in the new European Union member.

The conservative HDZ party, which has ruled Croatia for 16 of its 22 years of independence, became the first political party sentenced for corruption.

The trial, which started in April 2012, was part of an anti-fraud drive to boost Croatia's attempt to join the EU, which it did in July last year.

A Zagreb-based political analyst, Davor Gjenero, said this: "This ruling is very important. It sanctions for the first time a political party's illegal funding and this will have along-term effect on political financing in Croatia."

The Zagreb county court gave Mr Sanader, already sentenced to ten years jail in another corruption trial in 2012, a new nine-year sentence.

The HDZ party, now in opposition, was ordered to pay back about 29 million kuna (€3.79m).

Judge Ivana Calic, said Sanader and four other people had conspired to secure illegal funding for the HDZ party from public firms from 2003 to 2009, when Sanader quit the government without explanation.

He was later expelled from the party and fled the country, but was arrested in Austria and sent home for trial.

The HDZ party said it would appeal the verdict.

Along with Sanader and the HDZ, the party's former treasurer, accountant and spokesman were also found guilty and sentenced to shorter prison terms.