The battle over the European treaty continues – creating difficulties for all three of the main parties. But the battlegrounds are likely to be different from what the opponents of the treaty hope and claim.

Ratification itself should be pretty straightforward now that the Commons has rejected a referendum. Claims by some right-wing bloggers and the “I want a referendum” campaign that the outcome could be different in the Lords show no understanding of the second chamber. To take a naive, mechanistic view that if the Liberal Democrat peers were ordered to abstain, then the Tories, and a few crossbenchers, might be able to outvote Labour is nonsense. For a start it assumes, falsely, that peers vote as a block, and with as high a turnout, as MPs do.

Does anyone seriously think that pro-European Conservative peers such as Lords Howe, Brittan, Patten of Barnes and Garel-Jones will vote for a sceptic-backed referendum? They, and a good many more Tory peers, are likely not just to refuse to back their party line but to vote against a referendum.

Similarly, many Liberal Democrat peers, notably the former SDP contingent, will vote against a referendum, not abstain. Admittedly, some Lib Dem peers will vote for one, as will a number of Labour peers. The argument that the debate has been curtailed in the Commons will count. But the odds are that a referendum will be heavily defeated.

The real battle will be elsewhere. This is not just about the damage to Nick Clegg’s leadership and Lib Dem divisions, which will overshadow his spring conference this weekend. As Philip Cowley, of the University of Nottingham, has noted, David Cameron suffered as big a split, the largest on the Bill, as Mr Clegg, but no one noticed. Forty-five Tory MPs backed Bill Cash’s amendment that nothing in the act shall affect the supremacy of Parliament. This was not quite a rebellion since there was a free vote, but the Tory front bench abstained.

Much more serious for the Tories is what happens after the treaty is ratified. The official Tory line is “we would not let matters rest there”, whatever that means. But there is strong pressure from the Tory rank-and-file for an incoming Conservative government to hold a retrospective referendum. Such a vote would reopen Britain’s EU membership, as many activists want and the leadership fears.

For Labour, the Commons rebellion was not nearly as large as on other issues, confirming, as Professor Cowley argues, that Europe does not divide the party. The worry for Gordon Brown is whether Tory charges about him betraying Labour’s 2005 manifesto pledge on holding a referendum on the old constitution stick with voters, despite claims that the Lisbon treaty is different. However, the latest Ipsos MORI poll shows that only 3 per cent of voters regard Europe as among the most important issues facing Britain. It is all really about trust: whether the row fuels public doubts about Mr Brown.

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