Responding to comments from former SNP advisor Andrew Wilson that a future case for independence "should not include north sea oil", Scottish Liberal Democrat leader Willie Rennie warned that the economic case for independence is weaker than ever.
Mr Rennie said:
"The economic case for independence is weaker than ever with the plummeting oil revenues.
"The SNP have no answers so they resort to stating the blindingly obvious.
"Of course oil is not a bonus and now it hardly raises any revenues at all so we face a £15billion black hole.
"The SNP will need to explain which public services will be cut to pay for independence."