SCOTS will not be told the cost of setting up an independent Scotland before they go to the polls in September's referendum, the Scottish Government has admitted.

The First Minister's chief political spokesman said no figure for the cost of creating new government departments and public bodies had been calculated.

He insisted the final bill would depend on negotiations with the rest of the UK following a Yes vote - and claimed ministers had not asked civil servants to work out an independent Scotland's overall start-up costs.

The revelation came after Mr Salmond said £250 million was a "reasonable" estimate of the total cost.

Yesterday, following claims the figure was unrealistically low, he came under pressure to publish behind-the-scenes work on the costs that was prepared by government officials two years ago. Mr Salmond ducked the calls during First Minister's Questions.

Pressed later, his chief political spokesman said: "The work taken forward by the Scottish Government informed the White Paper. We have published in the White Paper the shape and structure of an independent Scotland and the government apparatus it would require, as we see it."

He said the final cost could not be known until negotiations over the future of UK-wide institutions, such as the Department for Work and Pensions and the Passport Agency, were completed. He added: "You can't finalise the start-up costs until you have a fair division of the assets."

He defended Mr Salmond's £250m figure - which was based on comments in the press by London School of Economics expert Patrick Dunleavy - as a "sensible, common-sense" estimate based on "an understanding there would be a few more Scottish Government departmental responsibilities".

In a leaked Cabinet briefing dating back to 2012, before the publication of the White Paper, Finance Secretary John Swinney indicated that civil servants were working on the costs.

Mr Salmond's chief spokesman yesterday said the civil service work may have taken the form of "emails and jottings" and was never intended to produce a full document or an overall cost.

Scottish Conservative leader Ruth Davidson said: "By John Swinney's own hand we know civil servants were working on preparing start-up costs for an independent Scotland. It's astonishing the Scottish Government now claims this work never existed."

Scottish LibDem leader Willie Rennie said: "People will doubt what the First Minister's spokesman said as John Swinney told the Cabinet that work had already started. So where is that work? Was it completed? And if not who ordered it to stop?"

Scottish Labour's finance spokesman Iain Gray said: "The Scottish Government expects Scots to vote for their future with no idea of what it will cost them if they choose independence."

The White Paper does not put a figure on start-up costs but says it would amount to "a small proportion of an independent Scotland's total budget".

The Scottish Government says an independent Scotland would be entitled to a £110bn share of the UK's estimated £1.3 trillion assets.