Prime Minister Gordon Brown branded wildcat strikes indefensible as he sought to defuse a row over foreign workers and stop industrial action spreading across Britain this week.

Brown urged strikers at Britain's third-largest oil refinery not to continue their action on Monday, after protests over the employment of Italian and Portuguese workers spread Friday to energy facilities nationwide.

In a BBC television interview broadcast Sunday, he also sought to explain his "British jobs for British workers" pledge, made in October 2007, that has been a focal point of the wildcat walk-outs.

European Union law enshrines the right to the freedom of movement for workers between member countries.

Brown said: "When I talked about British jobs, I was talking about giving people in Britain the skills, so that they have the ability to get jobs which were at present going to people from abroad, and actually encouraging people to take up the courses and the education and learning that is necessary for British workers to be far more skilled for the future."

Asked for his message to people considering wildcat strikes on Monday, he said that was not "the right thing to do and it's not defensible.

"Where there are jobs in this country, we need people with the skills, developed in this country, and that's why we're increasing apprenticeships during this difficult period.

"People are worried about what's happening to jobs in every part of our country."

Brown said he was determined to take quick action to save the jobs that can be saved.

"We've made some arrangements to do so. Where people lose their jobs, we help them back in to jobs as quickly as possible."

The dispute stems from French oil company Total's award of the contract to build a new desulphurisation unit at the Lindsey refinery in eastern England to Italian company IREM.

Around 100 Italian and Portuguese workers, living on barges in nearby docks, work there and are set to be joined by 300 more next month. Trade unions claim Britons were not given any opportunity to apply for the positions.

The government has asked ACAS, the body for resolving employment disputes, to investigate the facts quickly and report to the government, employers and the trade unions.

In a statement, Total stressed it had never discriminated against British companies or workers here, saying that where sub-contracts were let, firms from both Britain and elsewhere in the European Union can bid for work.

"It is legal for sub-contractors to supply their own employees but, where vacancies are advertised, we will work with our sub-contractors to ensure that British workers are considered in the same way as anyone else," it said.

Business Secretary Peter Mandelson, formerly the EU's trade commissioner, warned Saturday: "It would be a huge mistake to retreat from a policy where within the rules, UK companies can operate in Europe and European companies can operate here.

"Protectionism would be a sure-fire way of turning recession into depression."