Alan Trench: Many high hurdles to get over before such major changes can be made

There, Clegg went for a house of 300 members, largely or wholly elected, using the single transferable vote, for 15 year terms. The key differences are that the joint committee wants a house of 450, and a referendum before there is any change.

Strong opposition from a number of Conservative MPs to big-bang Lords reform creates a real danger of a parliamentary impasse. The issue has become totemic for Lib Dems, especially after the loss of the AV referendum. The prospect of a referendum on an issue that interests few voters, perhaps after a long and bitter battle, adds a further high hurdle to securing change. That itself may be a strong argument for a more incremental approach.

The overwhelming merit of Clegg’s proposal as endorsed by the joint committee is that it offers a chance of preserving the independence members of the upper house currently enjoy. Members of an upper house with tenure for 15 years and no chance of re-election would be largely immune to control by whips if they wished, perhaps even more so than peers are at present. If the elections were to produce people of character and ability, they would have the chance to make a good deal of the position they would have.

The problem is that political parties will inevitably wish to control the selection of upper house candidates, as well as run election campaigns. Even with STV, there will be serious barriers for independent candidates before they can be elected. Moreover, if election to the upper house is seen not as the culmination of a career of public service but the start of a career in elected politics (as happens in some countries, such as Japan), the upper house could just turn into an ante-chamber to the Commons. The joint committee appears not to have considered this issue. A further effective guarantee of members’ independence would be to disqualify them from sitting in the Commons for the full duration of their term and for five years thereafter.

What we also do not know is how Lords reform will relate to other features of the changing UK constitution. Much remains on the table, including “devolution more” for Scotland, changes in response to the West Lothian Question, or the new equally-sized Commons constituencies. The coalition’s piecemeal approach means the constitution is becoming even more disjointed than it was. Last week the Commons political and constitutional reform committee announced an inquiry into whether there should be a “UK constitutional convention”, something Welsh First Minister Carwyn Jones has also called for. Such a convention would be highly problematic, but it would at least create a more structured and inclusive process to consider the wide range of issues now on the table.

• Alan Trench is an honorary fellow at the School of Social and Political Science, University of Edinburgh