The defeat of electoral reform a year ago means that Nick Clegg is determined to secure reform of the House of Lords in this parliament. Clegg needs at least one defining constitutional change to persuade his party that the coalition has been worth it. Indeed, he recently heightened the stakes by suggesting that the Lib Dems could vote down the proposed boundary changes if the Tory backwoodsmen veto Lords reform.

The Queen's Speech in May will contain a bill proposing the creation of a new second chamber in which 80 per cent of members are elected and 20 per cent appointed. But Clegg now faces a further obstacle to reform. A joint committee of MPs and peers has unexpectedly called for a national referendum to be held on the proposed changes. Neither of the coalition parties supports a referendum but Labour, however, does. The shadow justice secretary Sadiq Khan commented yesterday:

The public should have the final say on major constitutional reform, a position the Tory-led Government followed with the referendum on the alternative vote, and its votes in towns and cities for directly elected mayors.

Today's Independent reports that Clegg will oppose a referendum [which would delay and possibly prevent reform] on the grounds that all three of the main parties advocated Lords reform in their general election manifestos. But Labour will point to the fact that it also backed a referendum in 2010. Until recently, the British electorate had little experience of referenda. The AV referendum was only the second to be held on a national level [the first was the vote on EU membership in 1975]. But that vote - and those forthcoming on directly-elected mayors - has set a precedent. Once the possibility of a referendum is raised, it is hard to argue that the people should be denied a say. That is the challenge Clegg now faces.