THE European Union Referendum Bill is to be David Cameron's Government's priority measure when its first Bills are published next week, according to a senior Whitehall source.

The swiftness of the Bill's publication and start of its process through Westminster might suggest that the Prime Minister wants to fast-track the measure through Parliament to enable the referendum to take place next year and not in 2017 as originally planned.

It is expected that, along with the Scotland Bill to implement the recommendations of the Smith Commission on extra powers for Holyrood, the EU Bill will be published on Thursday May 28, the day after the Queen's Speech when the Tory leader will set out his majority Government's legislative programme.

The source said: "The EU Referendum Bill will be the first to be laid." It is expected that debates on the Bill will begin before MPs rise for the summer recess.

This is also expected for the new Scotland Bill with the detailed Committee Stage taking place in July. The Herald understands that it is the UK Government's intention to have the Scotland Bill on the Statute Book by early 2016 - in time for the next Holyrood election.

David Mundell, the Scottish Secretary, described the Scotland Bill as a "priority measure" and noted how there were some changes to the original draft to reflect fully the Commission's recommendations, particularly in the area of welfare.

However, he stressed that the SNP Government proposals put forward for extra powers on top of the Commission's recommendations would be considered later, recognising there would be an "argument about additionality".

Yet, it is not thought at this stage that the UK Government is minded to accept any of the extra "priority devolution" measures such as on employment law, business taxes, National Insurance and welfare, which First Minister Nicola Sturgeon has called for. Mr Cameron has also insisted in terms that his Government is opposed to giving Scotland full fiscal autonomy.

Mr Mundell is due shortly to talk to John Swinney, Ms Sturgeon's deputy, about the Scottish Government's proposals.