Evidence found of an attempt by Azerbaijan to try to buy votes during last year's competition in Sweden

Eurovision Song Contest organisers will ban countries guilty of vote rigging for up to three years after an inquiry found evidence of a failed attempt to fix last year's competition in Sweden.

The European Broadcasting Union, which runs the 58-year-old contest, announced a tightening up of the rules on Thursday in a bid to end accusations of bribery and block voting that have dogged the competition in recent years.

Azerbaijan was accused of trying to buy votes from jurors and members of the public taking part in the telephone poll during last year's event in Malmo, with Lithuanian students alleged to have been paid to dial in.

The EBU's inquiry concluded that attempts had been made to influence the vote but did not succeed due to security procedures already in place.

It said no evidence was found linking a participating broadcaster to the vote rigging, or that any of the broadcasters knew who was responsible.

The organisers said broadcasters would be banned for up to three years if voting irregularities were discovered to have taken place in their country.

Frank Freiling, chairman of the contest's governing body, known as the reference group, said: "Just as football clubs are in principle accountable for the behaviour of their fans, we will hold – on a case-by-case basis – participating broadcasters accountable and make them responsible to prevent voting irregularities in favour of their entry."

A Lithuanian website published a secretly-recorded film on the day of the Malmo final which appeared to show youngsters being offered cash by Russian-speaking men to back Azerbaijan, who last won in 2011.

Azerbaijan finished runners up last year with its entrant, Farid Mammadov, scoring a surprise 234 points. The former Soviet republic finished second to Denmark's Emmelie de Forest, with 281 points.

Great Britain, which last won in 1997 with Katrina and the Waves' Love Shine A Light, finished 19th on 23 points for Believe in Me, sung by Bonnie Tyler. It was marginally up on the 25th place (12 points) secured by Britain's entrant, Englebert Humperdinck in 2012.

The competition's voting system was changed in 2009 with a nation's points awarded on a 50/50 basis made up of a viewer phone-vote and jury verdict.

In September last year, the EBU announced new rules around the juries, including the publication of the names of the people taking part, in an effort to improve openness and transparency.

The Eurovision Song Contest's executive producer, Jon Ola Sand, told MediaGuardian: "The ban is up to three years and no-one should be in any doubt that we will act if we detect voting fraud.

"It is a drastic move but we are all in this together and we have to make sure nothing happens, it is not good for the brand. I have asked broadcasters, if you know something come forward and show me. If I have a smoking gun or evidence I can act, but I cannot act on rumours."

Sand, a Norwegian TV executive, said his first thought was that the video allegedly showing vote rigging was a hoax but that he now believed it to be true.

"I was irritated, angry about it. We did the investigation we could, but we don't have the tools or the methods of the police," he said. "We are confident that the broadcaster itself is not involved.

"We are now tightening the procedures on the jury voting, and the tele-voting, putting more responsibility on the broadcasters because we found a lot of them didn't even have a clue that this could happen. Our message to everyone is, if you are involved in acts like this, it could have a consequence, everyone will suffer."

The EBU has brought in accountants PwC to oversee the voting process, with every participating juror, and their vote, made public in an effort to halt further bribery allegations.

Sir Terry Wogan, who hosted BBC1's coverage of the event for 35 years, quit in 2008 after tiring of the block voting, in which neighbouring countries support each other, and complaining it had become too political.

Rules were changed the following year, introducing national juries alongside the phone vote.

Sand said: "As long as I have been with the contest there have been rumours about swapping votes and neighbour voting, all kinds of rumours. We try to do it as good as we can, and we introduced juries in 2009 to get rid of most of the neighbour voting, to balance it out.

"I don't mind that, I think it's good that people vote for countries they feel attached to. It's laughed at a lot in the UK but it's enormously popular, and in other countries it is taken very seriously. We have very good systems in place to detect voting fraud."

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