NICOLA Sturgeon will tomorrow accuse the Unionist parties of an "unacceptable" failure to deliver a common plan for more devolution, and say it reinforces the case that only independence can deliver the extra powers Scotland needs.

With only 200 days to go until the referendum on September 18, the Deputy First Minister will say that Labour, the Liberal Democrats and the Conservatives cannot guarantee change within the Union, and that meant "responsibility for the vast majority of Scottish taxes would remain at Westminster".

In a speech to the Scottish Council for Development and Industry, she will say: "While it is not surprising there will be no common offer to the people of Scotland, given that the parties cannot agree amongst, never mind between themselves, it is nevertheless unacceptable. The simple fact is only a Yes vote will secure the powers Scotland needs."

It was reported yesterday that Scottish Labour's devolution commission, which reports this month, has dropped its big idea of devolving income tax because of disagreements within the party.

Shadow defence secretary Jim Murphy urged the commission to take an "ambitious approach".

Scottish Secretary Alistair Carmichael said voters should use the 200-day milestone to ask what independence would mean for pensions, tax and the currency. He said: "We cannot afford to gamble with our nation's future."

The SNP also seized on a report by the Pensions Policy Institute to claim Westminster decisions were the wrong fit for Scotland.

It showed lower life expectancies in Scotland meant rises in the state pension age to 66, 67 and 68 would give Scots less than a third of adult life in retirement.

It also emerged yesterday that Yes Scotland is to embark on a make-or-break advertising spree to woo voters. The campaign, estimated to be costing up to £2.5 million, starts on March 10.

Better Together said the timing indicated a crisis with Yes Scotland, which despite a recent lift remains behind in the polls.