In a blow to the SNP's hopes of avoiding disruption to private pensions in the event of a Yes vote, the European Commission said cross border schemes must continue to be fully funded, with sufficient assets to cover their liabilities.
The National Association of Pension Funds warned yesterday the ruling would make many UK-wide schemes, which are billions of pounds in deficit, "much more expensive" to run if Scotland became independent.
The warning came as the body representing Scotland's financial services industry raised further questions about the consequences of independence.
In a briefing designed to help institutions with business strat-egy, Scottish Financial Enterprise said the creation of a new currency in an independent Scotland was "a real possibility". It also said the Scottish Government's blueprint for independence, the White Paper Scotland's Future, should not be seen as a "balanced or reliable guide" to what might follow a Yes vote and that its true consequences "cannot be known in any detail".
The Scottish Government dismissed both sets of warnings.
They came as the Yes campaign received a boost from a YouGov poll showing 45% of voters thought Chancellor George Osborne and other politicians were bluffing when they ruled out Alex Salmond's plan to share the pound in a curr-ency union with the rest of the UK.
Fresh fears about pensions were raised after the European Commission yesterday issued a new occupational pension funds directive.
Unexpectedly the new ruling said cross border defined benefit schemes, offered by many employers, must continue to be fully funded. It means many UK-wide schemes would have to find billions of pounds to plug financial black holes - or split into separate Scottish and UK pensions after a Yes vote.
Among the schemes affected would be the Universities Superannuation Scheme which has a £10billion shortfall.
Joanne Segars, chief executive of the National Association of Pension Funds, said: "The European Commission had been expected to relax these special cross-border requirements, but it has disappointed many observers by leaving this part of the pensions directive unreformed.
"The knock-on effect of this is that schemes with members both north and south of the border would become much more expensive to run if Scotland were to vote for independence."
A spokesman for the Institute of Chartered Accountants Scotland said the rules remained "a major headache" for schemes set to become cross border in the event of independence.
Labour's shadow pensions minister Gregg McClymont said: "It's now clear beyond doubt that independence puts the pensions of hard working Scots at risk."
The Scottish Government, however, remained confident a solution would be found.
A spokesman for First Minister Alex Salmond said: "It is an updated directive and doubtless it will be updated again. There have been strong signals from Brussels that they are intent on resolving this issue. A new Commission is taking office in October and we will continue to make the case with the new Commission."
When the potential problem emerged last year, the Scottish Government insisted schemes would be given a period of grace to become fully funded.
Scottish Financial Enterprise, meanwhile, the voice of the country's £7billion financial services industry, warned a new currency was a "real possibility" following the UK parties' decision to rule out the SNP's plan to share the pound.
SFE chief executive Owen Kelly said: " What we know for sure is that there are some major risks and uncertainties directly affecting the financial services industry in Scotland."
Finance Secretary John Swinney said: "SFE set out many similar arguments ahead of devolution about taxation and uncertainty which have been shown to be misplaced, but in any event this is simply a briefing note from SFE officials, and not the view of the industry or of organisations within it."