Gordon Brown is under growing pressure to protect British jobs
Gordon Brown does not regret promising "British jobs for British workers", a No 10 spokesman has said, amid rising unrest about the use of foreign labour.
The PM's pledge, at the 2007 Labour conference, was attacked by critics as unwise and even illegal as European law opens UK jobs to all EU nationals.
The slogan is now being used by protesters at refineries across the UK, angry at a plant using Italian workers.
No 10 said it was working hard to help British people fill job vacancies.
Speaking in Switzerland where he is attending the World Economic Forum, Mr Brown said he understood people's anxieties about jobs as the recession bites and the government would do everything it could to help people find work.
Pat McFadden, minister for employment relations, said Mr Brown had not meant UK firms would be encouraged to flout European laws on free mobility of labour when he promised "British jobs for British workers".
"What he's saying there is, I want to see the British workforce equipped for the jobs and skills of the future and that's precisely what the government is doing," Mr McFadden told BBC Radio 5 Live.
But environment secretary Hilary Benn said UK workers were "entitled" to an answer in cases where they were not being used by firms.
And the TUC said peoples' anxieties about their job security may boil over into "difficult disputes" in some areas.
The issue of foreign labour in the economy has intensified amid mounting job losses across industry and a fall in vacancies.
Hundreds of workers walked out of refineries across the UK on Friday, in protest at a French-owned plant in Lincolnshire's decision to bring in 300 Italian workers for a contract instead of using local staff.
Several of the striking workers brandished placards: "In the words of Gordon Brown. British jobs for British workers."
Mr Brown made the "jobs pledge" shortly after he became prime minister in his speech to the 2007 Labour conference.
Then, Mr Brown said the government would be "drawing on the talents of all to create British jobs for British workers".
Supporters said the remarks emphasised the need to ensure the long-term unemployed had the skills necessary to find work.
But critics said the comments were misjudged and were unenforceable under EU law which requires companies to consider applications for vacancies from EU nationals.
BBC political correspondent Carole Walker said Mr Brown's comments could come back to haunt him as more and more people found themselves out of work.
Downing Street said the contract at the Lincolnshire plant was agreed before the downturn at a time when there was a shortage of skilled labour in the construction industry.
A spokesman said EU laws worked both ways, allowing British workers to work across the EU, but stressed ministers would be meeting construction industry representatives to ensure they were doing all they could to support the economy.
Asked about the "British jobs for British workers slogan", he said: "I do not see a reason for regret in that the action we have taken has meant that we are now putting in place measures to ensure that British workers can have access to the vacancies that exist in the system."
Conservative MP Bill Cash accused Mr Brown of "doing nothing" to change European law to make sure British workers had priority in the UK.
He added: "When circumstances change, laws have to change with them.
"It is not protectionism to insist that where there is a British workforce, which is willing and available to do the job of the right quality, they should be given the right to do those jobs. "
There are also concerns some firms are opting for foreign labour because it is cheaper, with unions citing examples of some foreign-owned business refusing to employ British workers.
Unions said they would put pressure on ministers to ensure there was a "level-playing field" in the jobs market.
Derek Simpson, general secretary of the Unite union, said it was "unacceptable" if British workers found themselves excluded from work for financial reasons.
"It's not the question of foreign workers. It is the question that some of these companies ... are saying they will exclusively debar UK workers, they will not consider UK workers under any circumstances."
He called on Mr Brown to stop what he said could be illegal action by firms under European law.
The UK Independence Party, which campaigns for Britain's exit from the EU, said with unemployment nearing the two million mark, it "defied belief" that foreign workers should be taking jobs where there was huge demand at home.
It blamed EU rules which say projects over a certain size must advertise jobs throughout the EU.