Dennis Canavan, Chairman of Yes Scotland’s Advisory Board, has written to Alistair Darling, of the No camp, challenging him to back with proof his jam-tomorrow promises and claims in a new No poster campaign.
To be launched on Monday, the No campaign advert mentions more powers for the Scottish Parliament, something Mr Canavan is asking Alistair Darling to confirm by providing an example of three new powers.
The new phase of the Yes Scotland promotional campaign - which was launched at the beginning of March - goes live next week with a series of new billboard posters and newspaper adverts.
As the polls continue to narrow, the latest material from Yes stresses key arguments that Scotland "can, should and must" be independent.
Yes Scotland welcomes an ICM poll in Scotland on Sunday and a Survation poll in the Sunday Post today. The ICM poll shows the highest support for Yes so far in the referendum campaign - 48 per cent when "don't knows" are excluded. The Sunday Post poll records the narrowest gap between Yes and No of any Survation poll so far, and also shows that people regard the Yes campaign as the most trustworthy and positive of the two.