Previously the candidate had been battling against centrist Emmanuel Macron, who has an equal 22 per cent of the polling vote as Ms Le Pen.
But far-left candidate Jean Luc Melenchon shocked investors when he surged by over seven points in the polls with just over a week until the election.
Mr Melanchon is already calling for a referendum on EU membership should he come to power, which has rattled traders.
Kathleen Brooks from City Index said: “The risk is that the far-left and the far-right make it into the second round run off”.
The euro’s volatility is likely to continue in the lead-up to the first round of voting this Sunday, right through until the final run-off on May 7.
Pound sterling has been further buoyed by strong inflation data last week.
March’s rate of 2.3 per cent, released by the The Office for National Statistics (ONS), showed inflation holding steady.
Rising food and clothing prices were offset by lower airfares thanks to the Easter period.
Inflation stands at its highest level in more than three years, blitzing the Bank of England’s target.
Ruth Gregory, UK Economist at Capital Economics, said: “We think that CPI inflation will peak at just over three per cent before the end of the year.
“But we don’t think that that will panic the Monetary Policy Committee (MPC) into raising rates imminently.
“Given the uncertainty around the Brexit negotiations and the fact that there has been little sign of building domestic cost pressures, we continue to think that the Bank of England Monetary Policy Committee will hold off until the middle of next year before raising rates.”
