At Nicola Sturgeon’s lecture on Scottish independence on 13 February, she was asked about the 2015 general election, and how that might affect the timetable for Scottish independence.
If Scotland votes Yes this September, then the timing of the UK general election in May 2015 presents difficulties for the Scottish government and for the UK government. It presents difficulties for the Scottish government, because they propose an 18 month timetable for the independence negotiations, from September 2014 to March 2016, and the UK general election falls right in the middle of that. The negotiations will be very intensive, and involve every senior Minister in the UK government, with separate teams leading on finance, defence, energy, transport etc. If there is a change of government in the UK in 2015 all those ministerial teams would change; and the new Ministers might start to unpick what had been agreed so far. That could slow down what is already a very tight timetable.
The UK government will also be in difficulty if there is a change in 2015. It will be in particular difficulty if Scottish MPs hold the balance of power in the new Parliament. That is most likely to happen if Labour is the largest party in the May 2015 elections, but depends on Scottish MPs to form a government (as happened in 1964 and 1974). On the SNP timetable, those Scottish MPs would be short lived, and due to leave Westminster in March 2016, when Scotland becomes independent. If the removal of those MPs meant that the government was unlikely to command the confidence of the House of Commons thereafter, the government would be a lame duck government from the start.
Formally there is an answer to what would happen in March 2016 (if that is Independence Day, and the date when the Scottish MPs depart). It is provided by the Fixed Term Parliaments Act. Under that Act, if the government loses a formal no confidence motion, and no alternative government can be formed within 14 days, then fresh elections must be held. But that formal constitutional answer might not be a sufficient answer to the political difficulties facing the government from the outset.
We could have a ‘temporary’ or ‘transitional’ government for a period of time until Scotland formally leaves the union. Public sentiment in the rest of Britain is unlikely to be sympathetic to the idea that the Scots who are leaving the Union are ‘imposing’ a government on the rest of the UK (think of the headlines in the Sun and the Mail). Another twist is that the UK government negotiating the terms of Scottish independence would be responsible to a Westminster Parliament which still contains Scottish MPs. The UK government should be negotiating on behalf of rUK, the rest of the UK after Scotland has departed. But if Scottish MPs held the balance of power at Westminster, they might be able to ensure terms which were more favourable to Scotland.
For Ed Miliband being reliant on short lived Scottish MPs to form his first government would be a nightmare scenario. He will be praying even harder than David Cameron for a No vote in September.
The Constitution Unit Blog 
Good analysis. I’d add only one thing.
The historical data given on past Westminster elections as affected by the Scottish MPs are correct as they stand but they may no longer be a good guide to what might happen in 2015. That’s because the two main reasons why the Scottish MPs have rarely been critical to the formation of a government in London no longer apply, or at least only apply to a lesser extent than in most of the post-war period.
One is that for the period between the 1940s and the 1990s the Tories still held a double-digit number of Scottish seats (and in the 1950s famously took over 50% of the Scottish vote): the phenomenon of Labour holding an extraordinary 40 or 50 more Scottish seats than the Tories, which is where we are now at, makes the Scottish dimension affecting the overall contest between the parties at Westminster more likely than it was for most of the period since 1945.
The other reason why this used to matter less is that for decades after the War the two main parties scooped the overwhelming bulk of UK-wide votes and MPs between them, making large-ish majorities likely as the pendulum swung between red and blue. This again is now less the case. With the two main parties barely taking 70% of the vote, comfortable majorities (as we saw in 2010) have become less likely and winning margins at Westminster tighter. This in turn makes Labour’s recent advantage of 40-odd more Scottish MPs than the Tories potentially of much greater arithmetical significance.
I would say that for both of these reasons a repeat of 1964 or 1974 (or indeed 2010), where the Labour MPs from Scotland do affect the nature of the resulting government, is significantly more likely than the historical record might make it seem.