French presidential candidates Emmanuel Macron and Marine Le Pen exchanged insults, rolled their eyes and almost certainly did little to change the course of an election in their only head-to-head debate ahead of voting this Sunday.

The tone was set in the opening statement of last night's tete-a-tete, when Le Pen, a far-right eurosceptic who trails in the polls by about 20 percentage points, opted against setting out her vision for France in favor of a tirade of personal insults against the independent centrist.

Le Pen accused him of being a stooge for the unpopular socialist government, a "smirking banker" who wanted to sell France's assets and the poster boy for "savage globalization" and the "Uberisation of french society."

Macron responded in kind. "Your strategy is to tell lots of lies, to say everything that isn't working and offer nothing."

From there, incredibly, the tone of the debate headed down hill.

"It was a boxing match not a debate," said David, a photographer from Paris's western suburbs. "She just attacked and attacked."

The marathon two-and-a-half hour confrontation was watched by about 16.5 million people, according to the French daily Le Figaro. Snap polls following the debate suggested that 65% of viewers regarded Macron's performance as the better of the two - a figure that reflects polling for the two candidates which has put Macron's support at about 60%.

What little policy debate emerged from the encounter tendered to center on Europe and state financing and played to Macron's strengths and Le Pen's weakness.

Le Pen's plan to introduce a dual currency for France, where the 'new franc' would be used internally, while the euro would continue to be used for international trade and by the central bank was ridiculed by Macron, a former finance minister and Rothschild's banker.

"Big business can't pay in euros on one side and pay its employees in francs in France. It is ridiculous Madame Le Pen.," said Macron. "Our debt, will it be paid in euros or francs?...It is a project of death."

Le Pen responded by claiming that French companies had been able to pay in either euro or francs from 1993 until the euros introduction in 2002, appearing to confound the European Currency Unit, which was a basket of currencies used as an accounting measure by the European Community, for a physical currency.

She accused Macron of launching "a scare project" and suggested that Britain's economy had prospered since it voted to leave the European Union. Britain's economy grew 2% in 2016, but saw growth fall to 0.3% in the fourth quarter, post the Brexit vote. Britain has not yet left the European Union and never adopted the euro as its currency.

Le Pen was soon back on more comfortable ground, returning to insults and insinuations. At one point she suggested that Macron might have an offshore bank account, though offered no proof. She also railed against France's "politicized" judiciary suggesting it was responsible for an investigation into her own tax affairs.

She capped it all with a rehearsed 'zinger' claiming that France will be governed by a woman after this election no matter what the result, with the only options being her or Angela Merkel of Germany.

Macron retorted, calling Le Pen the "high priestess of fear" and her party, the Front National, "a parasite that feeds and nourishes fear."

"Your words show that you lack the dignity to be the defender of our institutions," he said.

With polls suggesting that about 30% of eligible voters are prepared to destroy their ballot rather than vote for either candidate, it remains to be seen if the Wednesday's bare-knuckled debate can bring them to the ballot box.

"The next person who talks to me about abstention or destroying their ballot, I am going to make them re-watch this debate 100 times," said Fabrice, an executive at a French printing company.