Many thanks to @Chersfrozenface
I'm putting some extracts from the document here. Bold is mine.
Whatever our personal views, we should frankly recognize that these proposals were put before the country at the recent General Election and that the people of this country, with full knowledge of these proposals, returned the Labour Party to power. The Government may, therefore, I think, fairly claim that they have a mandate to introduce these proposals. I believe that it would be constitutionally wrong, when the country has so recently expressed its view, for this House to oppose proposals which have been definitely put before the electorate. (HL Hansard, 16th August 1945, vol. 137, col. 47)
Because of the large Labour majority in the Commons in 1945, it was therefore possible for us who belonged to the opposition to make it our broad guiding rule that what had been on the Labour Party programme at the preceding General Election should be regarded as having been approved by the British people. Therefore ... we passed all the nationalisation Bills, although we cordially disliked them, on the second reading and did our best to improve them and make them more workable at committee stage. Where, however, measures were introduced which had not been in the Labour Party Manifesto at the preceding Election, we reserved full liberty of action. (HL Hansard, 4th November 1964, vol. 261, col. 66)
Cranborne reckoned that it was not the duty of the House of Lords to make our system of government inoperable. Nor, he considered, was it justified that the Opposition peers should use their voting strength to wreck any measure which the Government had made plain at a General Election that they proposed to introduce ... [this] meant that the Lords should, if they saw fit, amend, but should not destroy or alter beyond recognition, any Bill on which the country had, by implication, given its verdict. The Lords, in other words, should not frustrate the will of the people. I doubt if this amounted to a formal constitutional doctrine but as a way of behaving it seemed to be very sensible ... Cranborne had to allow some robust words and tactics, but still retain sufficient control to prevent the passing by the Opposition of ‘wrecking’ amendments – as opposed to those which could perhaps draw a good deal of the poison from a Bill without seeming to destroy it utterly. There was, of course, argument about what constituted a wrecking amendment and what did not: but, by and large, the Salisbury strategy worked and the Salisbury convention – of no wrecking amendments – was observed. To this day the convention continues ... Later in life I applied the same convention myself. (Lord Carrington, Reflect on Things Past: The Memoirs of Lord Carrington (1988), pp. 77–78)
The definition of the Salisbury Doctrine:
The Salisbury Doctrine, or "Convention" as it is sometimes called, emerged from the working arrangements reached during the Labour Government of 1945-51, when the fifth Marquess of Salisbury was the Leader of the Conservative Opposition in the Lords. The Convention ensures that major Government Bills can get through the Lords when the Government of the day has no majority in the Lords. In practice, it means that the Lords does not try to vote down at second or third reading, a Government Bill mentioned in an election manifesto.
So it seems to me the question is, does the Labour Party's performance so far meet the requirement 'that the people of this country' have 'full knowledge of these proposals'? I'd say no, we don't have full knowledge of what the Labour Party proposes to do, so it doesn't meet the requirement..