There is an inherent conflict between defending the supremacy of the Commons and making the composition of the Lords more “legitimate”, less aristocratic and more democratic. Before the removal of all but 92 hereditary peers in 1999, the power of the Lords to oppose the will of the Commons was generally used with restraint (though in a pro-Tory direction).

Formally, the Lords can delay all non-financial legislation by at least a year, though it has no role over taxation Bills. If used regularly, this could make life impossible for a government. But since 1999, the predominantly appointed Lords has believed it has more legitimacy and has defeated the Government twice as many times as before then.

This contradicts the silly talk of Tony Blair making the Lords impotent. The reverse is true: despite the increased numbers of Labour peers, they can still easily be outvoted by the Tories and Liberal Democrats combined, as has been seen in the endless ping-pong over the Identity Cards Bill. This was eventually resolved last night after a deal (involving just a small concession by the Government) that was accepted by the Tories, though not by the Lib Dems.

The existing self-imposed contraints are already under strain. The Lib Dems have repudiated the Salisbury convention under which the Lords does not block Bills that have appeared in a party’s manifesto at the previous election. They claim that Labour now lacks a mandate because of its low share of the overall vote last May. This is slippery ground for any party recognising the supremacy of the Commons. Lord Strathclyde, the Tory leader in the Lords, has been more cautious, saying that the convention should still apply, except, crucially, to Bills seeking to change the powers of the Lords.

Imagine the position if more than half, or even two thirds, of the Lords were elected. Such a chamber could easily claim a democratic mandate and challenge the Commons, leading to frustration and deadlock. That is why the Government wants formal limits to the powers of the Lords, notably reducing its scope for delay to a few months, and codifying existing conventions. Tory peers oppose such changes.

The link between composition and powers has been the stumbling block in the past, as Labour MPs have always been wary of a stronger Lords.

Any optimist about reform should read a fascinating paper by Chris Ballinger, of Brasenose College, Oxford, to be delivered to next week’s conference of the Political Studies Association. He highlights the two postwar interparty conferences on the Lords, in 1948 and 1968. In the first case, the parties were too far apart, while in the second, intriguingly, the small working party did make progress (on powers of the Lords, with Lord Carrington, the Tory leader, conceding a delay of six months from the time of disagreement between the Houses). But the negotiators went farther than backbenchers would accept.

Mr Ballinger’s conclusion is that a consensus will be almost impossible to reach because of differences about the role of the Lords. But any attempt needs to involve much more than party leaders since backbenchers in both Houses can easily block reform plans.

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