YES Scotland has come under fire for claiming the costs of establishing a go-it-alone state would be less than £300 million.

In a video issued yesterday, the pro-independence campaign claimed the "initial start-up costs" of breaking away from the UK would be covered by saving £250m on Trident and a further £50m from ditching Westminster.

But the sum – equivalent to just 1% of the Scottish Government's annual budget – was dismissed by pro-UK parties as "simply untrue".

Yes Scotland made the claim in a video entitled "Ten things to tell your friends about an independent Scotland".

It said: "With independence we'd save on some UK spending so the initial start-up costs would be met by the £250 million annual saving from the UK's nuclear weapons and the £50 million annual saving from no longer paying for politicians at Westminster."

An independent Scotland would have to create government ministries, regulatory bodies and embassies and reconfigure military bases to meet the needs of the proposed defence force.

The SNP Government has not yet put a figure on start-up costs, but Finance Secretary John Swinney has privately warned the annual cost of operating a new tax-collection system would be between £575m and £625m.

In a statement issued on behalf of the Better Together campaign, Scots Tory deputy leader Jackson Carlaw said it was "simply untrue" the apparatus of a new state would cost as little as £300m.

He said: "Many new agencies would need to be established and paid for if we go it alone and this would cost hundreds of millions of pounds.

"For the nationalists to say that it could be paid for just by not replacing Trident is a bare-faced attempt to deceive the people of Scotland."

Ken Macintosh, Scottish Labour's finance spokesman, said: "According to Yes Scotland's back-of-the-fag-packet sums, it would cost less to create an independent state than it did to build the Scottish Parliament."

A Scottish Government spokesman said: "Any one-off costs of transition would be completely outweighed by the benefits that would accrue to Scotland as a result of independence.

"Scotland is a wealthy country that is well able to be independent. Scotland would be ranked eighth in terms of GDP per capita in the OECD, compared to the UK's 16th, and we have generated more tax receipts per person than the UK for every one of the last 30 years."

The row came as Alex Salmond's economic advisers hit back at criticism of their plan to keep the pound in a currency union with the UK. The move prompted a warning last month from Chancellor George Osborne that the UK was "unlikely" to agree a deal.

But the Scottish Government's Fiscal Commission Working Group yesterday insisted: "We believe an agreement to retain sterling as part of a monetary union can be reached and that there is flexibility regarding the specific institutional arrangements."

The group, led by former Scottish Enterprise chief Crawford Beveridge, repeated its call for talks with the Treasury on the plan, and its claim that a currency union was in the "overwhelming economic interests" of the UK and an independent Scotland.

The Treasury immediately ruled out "pre-negotiation of the terms of independence" before the referendum.

A spokesman said a currency union was "second best" for Scotland and the UK and added: "The Fiscal Commission wants Scotland to keep the pound; the best way to ensure this is for Scotland to remain inside the United Kingdom."

Economists Jim and Margaret Cuthbert, whose work is often cited by the SNP, also criticised the plan. They said an independent Scottish Government's economic policies would be heavily constrained by a pact with the UK, and the plan "fell far short of any meaningful concept of independence".