By Chris Mason
BBC News, Brussels
The European Union is being forced to defend one of its founding principles - the free movement of labour between its member states - as unrest among workers across the UK continues.
UK members of the European Parliament are debating precisely how, if at all, existing rules might have to change to end the dispute at the Lindsey oil refinery in Lincolnshire which has led to various wildcat strikes across the UK.
The row in Lincolnshire centres on the legitimacy or otherwise of the oil firm Total hiring labourers from Italy and Portugal.
And so at the heart of the dispute is the EU's rule book - a document that would make your telephone directory at home look like a mere postcard.
The so-called Acquis Communitaire is around 80,000 pages long, and right up there among the opening principles is the free movement of labour.
It was in the Treaty of Rome back in 1957 when the Common Market or European Economic Community, as it was then called, was set up - and so when Britain signed up in 1973, the country signed up to that rule too.
Here in Brussels there is widespread support for that founding principle - not least because of the perceived alternative.
"Protectionism will kill the economy stone dead," Andrew Duff, the leader of the European Liberal Democrat group and MEP for the East of England says.
The European Commission agrees. Johannes Laitenberger from the Commission told the BBC he had sympathy for the workers.
The strikes continued despite freezing weather conditions
But he said: "The internal market is actually our best platform to maintain a high level of employment in the European Union.
"All the evidence from past crises shows that the moment you enter a spiral of closing borders to each other, all will be the poorer and will have less employment."
The complicating twist here, though, is that it is not just to the opening pages of the European Union rulebook you have to look in this dispute.
Rules such as the Posted Workers' Directive and legal challenges to it also play their part - and prove confusing, as one Labour MEP admits.
"Even if Total have given guarantees that they will not exclude UK workers, or undercut UK conditions, recent European Court of Justice cases have for months now thrown doubt on how such companies will behave in the future," Claude Moraes, Labour's European spokesman on Employment and Social Affairs tells me.
"These judgments are getting the balance badly wrong."
In short, he feels that locally negotiated collective agreements - struck up between unions and firms - are being disregarded, albeit legally, by multinational firms, especially those hiring subcontactors.
"This is fear, not xenophobia, we are seeing in Lincolnshire and elsewhere," he says. "And you can see why it's happening."
His solution is a pan-European agreement - formal or otherwise - that would ensure companies do abide by local collective agreements.
Mr Moraes, an MEP for London, is concerned without this the next major row on the issue could be at the Olympics development site.
"This is the biggest construction project in the UK probably since the Channel Tunnel was built, and the same issues will be there too."
Critics though question the practicality of any new pan European agreement.
Malcolm Harbour is a Conservative MEP for the West Midlands and speaks for the party on the internal market.
"It's not Europe's business to be getting involved in collective agreements in particular industries," he told the BBC.
But he adds: "Unions are entitled to ask subcontractors about the deals they've signed other workers up to."
The view from the UK Independence Party here is more blunt. "Past governments sold us, sold the British worker, down the river and unless we get out of this prison of nations there is absolutely nothing anyone can do about it," says leader Nigel Farage, an MEP for the south east of England.
Meanwhile officials here in Brussels are well aware they have been here before. In France in 2005 there was a major political row about Polish plumbers being perceived to 'steal' French jobs.
In a referendum France held later that year on the European Constitution, voters rather loudly said 'No.' Some say the earlier dispute over jobs played its part.
Now, in 2009, the European Union is still mopping up the administrative mess that vote left it in.
Britain might not be about to hold a European referendum, but there is an awareness here of what is at stake in this dispute.