Eurosceptics were condemned yesterday for saying that a letter-bomb campaign against European politicians was the "price of forcing a political ideal on people".
The UK Independence Party, which is campaigning for Britain's withdrawal from the European Union, said it could "understand the reasons behind" the attacks on EU officials.
Nigel Farage, the party's MEP, warned of an "accelerating wave of violence" if groups opposed to the EU were "denied democracy".
Police are searching for the terrorists responsible for sending a spate of letter bombs over the past two weeks to European politicians and officials in Manchester, Frankfurt, Bologna and Brussels.
The UKIP was criticised by Gary Titley, the leader of Britian's Labour MEPs, who was the target of a letter bomb on Monday. He said: "The party that makes excuses for would-be murderers in the middle of a terrorist campaign against the European Parliament deserves to be shunned by all democrats."
Sir Menzies Campbell, the Liberal Democrat foreign affairs spokesman, said: "Nothing, but nothing, justifies actions of this kind and politicians committed to the democratic process should be unequivocal in their condemnation."
UKIP said that it "deplored" the bombing campaign. But it added: "Nigel Farage said that this prediction was now coming true and that although the party deplored the bombs, it could understand the reasons behind them."
Mr Farage said: "We have spent 10 years warning that the route the EU has chosen for itself, to swallow up nation states without giving the people of Europe the final say, was destined to end in civil unrest and violence. We can only hope that the EU comes to its senses and listens to the people. If it fails to do so, then there is clearly a very real danger of an accelerating wave of attacks as more and more extremist groups resort to violence as they are denied democracy."
Mr Farage said he condemned the bombers, but said that he "understood the reasons" behind the campaign.
The devices are believed to have been posted in Bologna, where Romano Prodi, the European Commission president, was the target of three attacks. The campaign has been linked to an Italian anarchist group, although Italian police have been concentrating their investigation on pan-European anarchists.Reuse content