In early 1868, Mr Disraeli became the Prime Minister of a minority Conservative government. Mr Gladstone, leading the Opposition, took his opportunity and thrust a Bill to disestablish the Irish Church through the House of Commons. The then Marquess of Salisbury advised his fellow peers that:

“when the opinion of your countrymen has declared itself, and you see that their convictions – their firm, deliberate and sustained convictions – are in favour of any course, I do not for a moment deny that it is your duty to yield. But there is an enormous step between that and being the mere echo of the House of Commons’

The measure had received no mandate from the people in a general election and the Lords threw it out. The doctrine of the popular mandate was born.

Lloyd George in November 1902 said of an Education Bill:

Let us take the election addresses during the last election… I venture to say that no important Bill …has ever been introduced into the House, at any rate within the last thirty or forty years, without a responsible leader of the Party indicating before the General Election that he was in favour of the problem being dealt with in a p[articular way.

In 1945, the Conservatives had 400, the Liberals 63 and Labour 16 peers, all hereditary, in the House of Lords. How was Mr Atlee to force through the Upper House his controversial programme, particularly the nationalisation of coal and steel? The respective leaders of Tory and Labour parties in the Lords, Salisbury and Addison, agreed that a ‘manifesto’ Bill as ‘foreshadowed’ in the governing party’s most recent manifesto, should not be opposed in the second chamber on Second or Third Reading and the Lords would not pass wrecking amendments. The Liberals were not consulted and were not a party to the so called Salisbury Convention. It was a private deal between the two main parties.

So it was that in the days of the Blair government, we argued that the Lib Dem group were not obliged to kow-tow to the Salisbury Convention. The argument got to the point where a Joint Committee was set up in 2006 to consider its application in modern times. The issue as to whether the Lords should give way to the Commons in the event of a minority government was considered.

Jack Straw, Leader of the Commons, told the committee that a coalition government involved a deceit on the electorate, in that you put forward a manifesto and determine what to do after an election rather than before.

My own view is that if any coalition or arrangement as in 1977 [with the Liberals] gains the support of the democratically elected House and is endorsed by a motion of confidence then the programme for which they gain that endorsement should be respected by this House.

David Heath and William Wallace for the Lib Dems argued that a minority government would only get its manifesto through by negotiation within the Commons, and by implication, not as a result of a popular mandate.

The Committee came to no conclusion on this point but did endorse the view expressed by Tom McNally, who was a member, that the Lords always retains the right to say, “No”.

The Convention recognises the special democratic claim that attaches to a manifesto commitment – but it has no force if it fails to gain majority support in an election. Nor is it possible to add together the separate commitments of two parties, especially if they are bound together by a compact based merely on confidence and supply. A shared Conservative-DUP Bill does not attract the Salisbury Convention, and on any view, Lib Dem peers are entitled to say “No”.

* Martin Thomas is a Liberal Democrat member of the House of Lords and the party's Shadow Attorney General