The UK Government is in the "last-chance saloon" over bank lending to small businesses, First Minister Alex Salmond said.
Mr Salmond said small and medium-sized firms in Scotland had got a "raw deal" from the Westminster initiative that was aimed at boosting bank lending.
He urged Chancellor George Osborne to use next week's Budget to help unlock finance for small businesses.
Addressing the Scottish Council for Development and Industry's annual forum, the First Minister said less than 5% of lending under the Project Merlin scheme had come north of the border, adding this was "far less" than Scotland's share of GDP.
Mr Salmond spoke out on the issue ahead of Wednesday's Budget and said: "The Chancellor has to act now to help banks help business.
"Without the necessary leadership from the Treasury, it is harder for banks to lend - and those who ultimately lose out are Scottish small businesses."
The First Minister said that "Scotland's share of Project Merlin lending to small and medium-sized businesses was 4.8%".
He blasted: "Scottish business got a raw deal from Project Merlin and the Chancellor has yet to show any sign of making cash more readily available.
"Back in November he announced the idea of a £20 billion 'credit easing' programme to enable cheaper loans. Scottish business is still waiting for the details.
"The UK Government is in the last-chance saloon on bank lending. Successive UK governments have had four years to address this issue. Next week, the Chancellor should finally do so."