David Cameron has been accused of "hypocrisy" by the SNP after the party's call for pre-election talks with Civil Service chiefs was rejected.

SNP leader and Scottish First Minister Nicola Sturgeon had written to the head of the UK Civil Service, Sir Jeremy Heywood, seeking discussions with Whitehall officials.

By convention, opposition parties can enter into confidential discussions on their key policies with senior civil servants in the run-up to a general election, but these must be sanctioned by the Prime Minister.

With opinion polls continuing to suggest that May's general election will result in a hung parliament, Ms Sturgeon argued that all parties with elected MPs could be in a position of power.

SNP Westminster leader Angus Robertson said Mr Cameron had refused to allow civil servants to have talks with the SNP.

It is reported that, in his letter to the First Minister, Sir Jeremy said the Prime Minister did not want to extend the offer of talks to parties that are only fielding candidates in one part of the country.

Mr Robertson said: "This is the height of hypocrisy from David Cameron. He reluctantly accepts the SNP should be included in TV debates because he wrongly thought it might help him avoid them, but he refuses to offer us pre-election access to the Civil Service to discuss our progressive policy agenda - an economic policy based on growth and jobs, cancelling Trident renewal, and four-nation consent before UK withdrawal from Europe can happen.

"The next parliament is going to be a hung parliament, and the Westminster parties are not going to get things their own way anymore. The SNP could well be in a position of influence in terms of how the UK as a whole is governed, and therefore it is in people's interests north and south of the border for us to be included in access to the Whitehall Civil Service."

Prior to the 2011 Holyrood election, former first minister Alex Salmond allowed pre-election talks to be held with all parties represented at Holyrood.

Ms Sturgeon had argued: "Given the likely continuance of a hung parliament situation in the House of Commons, I believe that, in advance of this general election, it is time for Westminster to move towards the higher, more inclusive standards which prevail in the Scottish Parliament.''