LONDON (Reuters) - Judges have ordered a re-run of a parliamentary election after a Labour MP was ruled to have smeared a Liberal Democrat rival in the first ruling of its kind for almost a century.

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Two judges declared void the result of May’s general election vote in Oldham East and Saddleworth after finding former immigration minister Phil Woolas guilty of illegal practices under electoral law.

Woolas said he would seek a judicial review of the decision, which if upheld would see him lose his seat and barred from standing for parliament for three years.

The Labour party said it was suspending Woolas because of the “seriousness of the facts of the case” and would not support any review or appeal of the judgement.

Speaker John Bercow is expected to make a statement to parliament on Monday on the matter. A re-run may have to wait until all legal appeals have been exhausted.

Any by-election would test backing for the LibDems following their decision to enter coalition with the Conservatives in May. Opinion polls show their support has plunged since they entered the alliance.

A re-run would also pit coalition partners against each other in a parliamentary ballot for the first time since the election six months ago.

Woolas had been named as shadow immigration minister by new Labour leader Ed Miliband, a position he now loses. Woolas had squeezed home in the election, holding on to his seat with a majority of just 103 votes over LibDem rival Elwyn Watkins.

But he was accused of attacking his opponent’s personal conduct and character by claiming that he courted Muslim militants who had advocated violence against the Labour MP.

He had suggested Watkins had refused to condemn such threats in pursuit of personal advantage. Both statements were untrue and Woolas knew them to be, the judges said, according to a report from the Press Association.

Watkins called the ruling a “victory for fair play and clean politics.”

“I hope this judgement makes it very clear that if you deceive your constituents you should be kicked out of parliament,” he added in a statement.