Large firms should sign up to a "tough code of conduct" to prevent them exploiting workers on zero-hours contracts, Ukip leader Nigel Farage has said.

He claimed cheap labour "flooding in from abroad" had left big employers in an increasingly powerful position to dictate terms for workers.

But Mr Farage acknowledged that the flexibility of zero-hours contracts, which do not guarantee regular work, suited some firms and employees and said he did not believe in banning the arrangements.

It is the latest sign of Mr Farage's efforts to target working class voters and woo support away from Labour in the run-up to next month's European elections.

Ed Miliband has promised Labour will regulate zero-hours contracts if he becomes prime minister and a Government review of the issue is expected to report in July.

In a Daily Express column Mr Farage said: "With so much cheap labour flooding in from abroad, giant corporations are in an increasingly powerful position to dictate terms and conditions for workers."

He added: "Unlimited immigration from eastern Europe and elsewhere has left many British working people pretty much defenceless against constant downgrades in their pay and employment conditions."

Mr Farage said that while having a zero-hours contract as an option was appropriate for some workers "having it as the only available form of work is quite another".

"And keeping people on zero-hours contracts for year after year when they aspire to stable employment so that they can provide for their families is something else again.

"I do not believe in banning zero-hours contracts. But I do believe there is a very strong case for expecting large employers to sign up to a tough code of conduct as to how they are applied.

"For instance, if an employee proves reliable enough to be working for a big company for a year or more then there should be an expectation that the company will offer him or her a permanent position."

Mr Farage said he did not blame multinational firms for trying to minimise their tax bills, but said they had to show responsibility to their workforce.

"I do not blame them for that - it is the responsibility of the authorities to set the tax regime after all," he said.

"But I do say that they should show more responsibility towards those on the shop floor. Often those kept on zero-hours contracts are women with major family responsibilities."

Mr Farage was praised as "charismatic" by the leader of France's far-right National Front, who said her "arms will be open" to Ukip if it wants to join together to fight the European Union.

Ukip told the BBC it is not interested in any deal with Marine Le Pen or her party, adding this is particularly because of "prejudice and anti-Semitism" in the National Front.

Ms Le Pen said she did not see UK Independence Party leader Nigel Farage as part of her movement and said an invitation for the party to be part of her campaign was no longer open.

But when asked if she would be open to work with Mr Farage in the future, she told BBC's Newsnight: "I am above personal considerations and any harm people try to inflict on us.

"My concern is the interests of the European people. My arms will be open as long as it's in the interest of the European people for us to join together in a common project to fight the European Union."

Asked what she made of Mr Farage, she said: "I think he's undoubtedly a charismatic leader. He has a message that people really want to hear and which is based on a correct reading of the situation.

"We do have our differences - for example, on the economy - there's no doubt about that.

"But I do think there is something he's missing, and that's the seriousness of the situation our continent finds itself in.

"If he understood how serious the EU's situation is, he would support the collaboration of all patriotic movements, and he wouldn't resort to tactics and strategy."