New EU Commission chief Jean-Claude Juncker told lawmakers not to insult him ahead of a confidence vote over the "Luxleaks" tax scandal, after French far-right leader Marine Le Pen compared him to gangster Al Capone.
Juncker faces a censure motion in the European Parliament on Thursday over revelations that Luxembourg gave tax breaks to many major global companies during his 19 years as prime minister of the tiny European duchy.
The motion was filed by a group of eurosceptic parties including Nigel Farage's UK Independence Party, Italian comedian Beppe Grillo's Five Star movement and French far-right leader Marine Le Pen's National Front.
Juncker, who only took over on November 1 as head of the commission, the EU's executive branch, vowed to tighten measures against tax avoidance across the 28-nation bloc.
"The commission that I have the honour of leading will fight tax evasion and tax fraud. Don't doubt my word," Juncker told a sitting of the European Parliament in Strasbourg, where Pope Francis is due to speak on Tuesday.
"I say to you very seriously: please stop insulting me.
"I will do what I have promised."
Juncker, a wily veteran of European politics, is almost certain to survive the vote as he has the support of all the major political groups in the 750-seat European Parliament.
A host of his senior commissioners -- who themselves also face the vote Thursday -- sat behind him in parliament in a show of support.
- 'Scandal will not go away' -
But the "Luxleaks" scandal has brought his reputation under scrutiny at an unwelcome time, when he is trying to focus on a huge 300-billion-euro ($380 billion) investment plan to boost the European economy, which he will unveil to parliament on Wednesday.
Far-right leader Le Pen poured scorn on Juncker's qualifications to take charge of any EU moves against tax evasion given Luxembourg's actions under his leadership.
"It's as credible as appointing Al Capone as head of the security and ethics committee," she said, referring to the notorious US gangster of the 1920s -- who was eventually prosecuted for tax evasion.
UKIP's Steven Woolfe said the allegations against Juncker were a "stain that will seep into the commission".
"This is an ugly tax scandal that will not go away," he said.
But Juncker can count on the support of most of the parliament, which is led by a "grand coalition" between his own centre-right European People's Party (EPP)and the Social Democrats of European Parliament President Martin Schulz.
"I am happy we will have the chance to vote on Thursday, I want the commission to continue with its work," said EPP leader Manfred Weber.
A vote against Juncker would harm efforts to shore up the EU's economy, beset by near-zero growth, high unemployment and the threat of deflation, warned Social Democrat leader Gianni Pittella.
"300 billion would go down the drain, we'd be cancelling the last chance to create jobs and combat the crisis," he said.