The last time Labour was the second largest party, but formed a minority government, was in 1924. The story is nicely told here by Lord Norton of Louth,
The government did not last long, from January to October when there was another General Election less than a year after the last.
MacDonald was appointed Prime Minister following Baldwin’s resignation, after he lost a vote of confidence when Parliament convened after the General Election of December 1923. There was only one Queen’s Speech, that of Baldwin’s government which was defeated on an amendment to it. After Parliament has been opened there is no need to re-open it, and so there is no need to call the sovereign back to read out another list of implausible claims about how transformative the government’s legislative programme is going to be.
MaDonald upon appointment gave a statement to the Commons, which is noticeable for two things.
First he set out no government programme. Instead he says
“I propose to introduce my business, knowing that I am in a minority, accepting the responsibilities of a minority.”
It is rather difficult to imagine Prime Minister Miliband being quite so diffident.
Second, he opens the statement with stories concerning members hiding in the lavatories:
“I have known bathrooms downstairs utilised, not for their legitimate purpose, but for the illegitimate purpose of packing as many Members surreptitiously inside their doors as their physical limitations would allow.”
It is also difficult to imagine Miliband wanting something like that to be the first thing he says in Parliament as Prime Minister of the United Kingdom. (The point of such hiding was and is to ambush the government by hiding the number of MPs who had turned up to vote.)
It seems likely that were Miliband to find himself in a similar position, some kind of legislative programme would be set out, equivalent to a Queen’s Speech, with a division of the House to determine whether the new government had the confidence of the Commons.
One possible straw to show what the future holds is also referenced by Lord Norton who quotes Robert Blake on the attitude of the Liberals in 1924:
“[The Liberals] supported Labour from an entirely independent position, with no written treaty, not even an informal understanding. Those Liberals who hoped for tacit, unspoken cooperation were soon disillusioned. There was none.’”
This may presage the Labour attitude to the SNP. Of course, in 1924 this was not an attitude that was constructive for either party of the left. By the end of the year Labour was out, and the Tories were back with a majority.