Marine Le Pen says she will seek to build a close relationship with the UK if elected president of France, and that her party, combined with Brexit, could hasten the collapse of the European Union.

In comments that contrast strongly with Francois Hollande's pledge to punish the UK for leaving the EU as a warning to others, the National Front leader said she wanted a new alliance with Britain.

"What is the point in punishing a country? It is senseless, unless you think the EU is a prison, and you are condemned if you escape. I want to rebuild our damaged relations with the United Kingdom.

"A people decides its own destiny. You cannot force a country to do something that is against its own interests, or against the democratic process," she told The Telegraph.

Polls by the newspaper L'Express puts Le Pen behind Francois Fillon 44 points to 56 points, and she pointed out that Brexit has been a "power weapon" for her party.

"In the past our adversaries have always been able to say that there is 'no alternative' but now we have had Brexit, and then Trump, and Austria," she said.

"A whole psychological framework is breaking down. I think 2017 is going to be the year of the grand return of the nation state, the control of borders and currencies," she said.

If elected, she would call on other EU members to agree to a break-up of the euro, impose trade barriers and control of post-Shengen borders. If her party's demands are not met, she vowed a referendum on EU membership and the single currency, which she hoped would also be opposed by other members.

"They may rally around France and agree to dismantle this structure together in an orderly way before it collapses in chaos," she said.

As the consequences of Brexit are also being pored over around Europe, the Irish prime minister Enda Kenny said his country's focus was to avoid a "hard border" when the British government triggers article 50.

Marine le Pen
Marine Le Pen, French National Front (FN) political party leader and candidate for the French 2017 presidential election, pictured on 5 February at a FN political rally to launch the presidential campaign in Lyon. Reuters

Kenny told the Institute of International and European Affairs in Dublin that as well as threatening Ireland's economy, it also raised the prospect of a fortified border between north and south.

"The Irish government will oppose a hard border, argue for free movement on this island, seek EU funding for cross-border projects and protect the rights of EU citizens, whether from North or South. But this requires the support of all strands of opinion if we are to succeed," he said on Wednesday evening (15 February), The Guardian reported.