The Labour Government came under fire from the SNP and Liberal Democrats after proposing no significant new powers for the Scottish Parliament.
The Government's submission to the Calman Commission on Scottish devolution said it was "keen" to see how the financial accountability of Holyrood can be improved.
But it gave no details on how this can be achieved, and this has been taken as a sign that Westminster is thinking of "assigned revenues" - a system of financing which First Minister Alex Salmond claims would give Holyrood less control over its finances than it has at present.