European leaders may have questions to answer after a pensions ruling which was widely expected to boost the case for independence failed to materialise, according the Scottish Government.

The European Commission said it will not review rules which require cross-border pension schemes to be fully funded, a directive which unionists say would land Scotland with a large pensions bill if it leaves the UK.

Speculation was mounting that the EC was due to relax solvency rules, potentially allowing schemes operating in Scotland and the rest of the UK to continue running a deficit in the event of a Yes vote.

But the EC said it will not review "existing quantitative solvency rules for occupational pension funds" in a directive released today.

Answering questions from journalists on the issue, a spokesman for First Minister Alex Salmond said: "If there appears to be a disconnect between what was being briefed heavily just a couple of weeks ago, as you rightly say, and what now appears to be a case you will have to ask the Commission what their reasons for that are."

The National Association of Pension Funds (NAPF) said the decision to uphold cross-border solvency rules came as a "big surprise", but the EC said it has consistently maintained the issue was not up for review.

Earlier this month, Chief Secretary to the Treasury Danny Alexander told pension fund managers that pensions would not be protected in an independent Scotland.

The Scottish Government accused him of "scaremongering in the full knowledge that the EU is on the point of resolving the issue of cross-border pensions".

The campaign to keep the UK together said today's directive "confirms that cross-border pension schemes must be fully funded".

Commenting on behalf of Better Together, Labour's shadow pensions minister Gregg McClymont said: "The EU has today confirmed that Scottish company pension schemes must overnight, if we leave the UK, fill a huge funding black hole.

"It's now clear beyond doubt that independence puts the pensions of hard working Scots at risk.

NAPF chief executive Joanne Segars said: "Today's announcement of a new EU pensions directive has major implications for pension schemes as part of the debate on independence for Scotland.

"The big surprise is that the EU will continue to require cross-border schemes to be fully funded - a significantly more demanding level of funding than is expected of single-country schemes.

"The EC 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 European Commission spokeswoman said: "In his statement in May last year, Internal Market Commissioner Michel Barnier said the proposal for a directive would not cover the issue of the solvency of pension funds.

"He commented that in light of the differing situations in member states regarding retirement products and pension funds, it would be necessary to continue technical work on the issue of solvency."

The First Minister's spokesman said there are still "very strong indications" that the solvency rules remain under review and pointed out that the current European Commission is on the way out.

He added: "It's not the first European Union directive on pensions. Far from it. It's an updated directive, the point being that these things get updated all the time and presumably doubtless will be updated again in the future.

"The point still stands that there are very strong indications from Brussels that this issue is being looked at seriously and they are looking at resolving the cross border issue.

"There's a new Commission taking office in October and we will continue to make the case to the new incoming Commission."