(DUBLIN) - A former Irish minister and Euro-MP was knocked to the ground after a public meeting on the European Union's controversial new Lisbon treaty, police and his party said Tuesday.

Labour Party MEP Prionsias de Rossa, 67 -- whose party backs the Lisbon Reform Treaty --- suffered cuts in the incident in the centre of Dublin on Monday night and was "very shaken," said a party spokesman.

Passions are rising ahead of a crunch Irish referendum expected on June 12 on the EU treaty. Ireland is the only member of the 27-nation bloc to vote on it, and could in theory scupper the treaty altogether.

Police confirmed they were probing the alleged attack. "We are investigating what appears to be an assault on Eden Quay," a spokesman told AFP.

Labour leader Eamon Gilmore condemned the assault and "anti-democratic tactics," saying he was "greatly shocked."

In a statement he said that when De Rossa left the meeting, "he was confronted by a group of men, some of whom had been present at the meeting and had spoken aggressively against the Treaty.

"One of the group shouted abuse at him through a loud-hailer. The group pursued Proinsias on the street.

"When he objected to being filmed by one of the group with a camcorder he was knocked to the ground and some of those involved sat on his back pinning him to the ground." Police then arrived.

He said there were about 100 people at the meeting in Liberty Hall and it became clear that "a minority of those present were not interested in any rational discussion and were present only to disrupt."

De Rossa was a member of the Dail (lower house of parliament) from 1982 to 2002. He was minister for social welfare (1994-97) and an MEP from 1989-92 and from 1999 to the present.

The Lisbon treaty was agreed in December 2007 amid much fanfare in the Portuguese capital and aims to prevent decision-making gridlock in the expanding bloc.

In June 2001 Ireland sent shockwaves through the bloc when it rejected the EU's Nice Treaty on institutional reform and enlargement. That decision was reversed in another referendum in October 2002.

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