Mary Ann Sieghart: MPs are getting ready for the fight of their lives

You don't see many MPs shivering in pavement queues and then storming Harrods to get the best bargains in the January sales. But over the next couple of years, they're going to have to start sharpening their elbows. For a little-noticed change in the law will make their jobs as insecure as the rest of ours. And they will have to fight their own party colleagues to hold on to their seats.

Not many voters have twigged, and even among many MPs, the implications have yet to sink in. But the consequence of the Coalition's plan to reduce the number of MPs and equalise the size of their constituencies is that almost every MP will have to be reselected before the next election. About 50 of them will find themselves without a job at all.

The Parliamentary Voting Systems and Constituencies Bill has its second reading in the House of Lords today. Until now, most argument has been about the referendum on voting reform. But the bill's plans to redraw the political map of Britain may turn out to be just as contentious.

The total number of MPs will be cut from 650 to below 600, and the effect will be felt most in Labour-held inner cities and the odd remote rural constituency. The bill says that every seat must have around 76,000 voters, with 5 per cent leeway on either side. If you were, say, Tristram Hunt, the Stoke-on-Trent Central MP, with just 60,995 registered voters, you might be looking nervously at your fellow Stoke-on-Trent MPs.

One of the city's seats will probably vanish, with its voters farmed out to the remaining constituencies. So, just like musical chairs, when the music stops, there will be a player left standing. And it is most likely to be a new MP, like Hunt, who hasn't yet had time to build local loyalties. Having been parachuted in close to the general election by party headquarters (and it doesn't help in the Labour Party to be called Tristram either), his position is even more precarious.

There are now lots of Labour MPs who thought they were ensconced in a safe seat for life and are suddenly feeling pretty nervous. If their constituency is abolished, they can't rely on being found another, as there will be fewer seats and many other colleagues in the same boat. And, because so many MPs stood down in 2010, there will be little natural wastage. This Parliament is full of the "new generation"; there aren't many bed-blockers left.

The prospect of having to fight for a new seat will damage relations between formerly friendly MPs. Normally members from the same city are allies. They travel up and down together twice a week and join forces to fight city-wide battles. Now, though, they are about to become rivals, as most big cities are going to lose at least one seat, maybe two. And the personal stakes are very high: these members' jobs, livelihoods and entire careers depend on being reselected. "The fear and loathing has yet to arrive," says one Labour MP. "But it will do. I think it will be quite a brutal process."

If Tories are feeling smug, though, they should think again. Although the party will lose fewer seats in all – about 13 to Labour's 25, according to a study by Democratic Audit – individually there will be barely an MP whose constituency boundaries don't change.

Because the Isle of Wight has so many voters – 109,966 – it is likely to lose about a third of them to a new seat, perhaps called Portsmouth South and Cowes. That will change the boundaries of the existing Portsmouth seats and then the ones around them, and so on. And it won't always be clear which sitting MP has a claim on each newly-drawn seat. So there will be some bruising fights.

Already members are doing their calculations. One young female MP recently sidled up to a much older one in a nearby constituency and said, "Of course, you won't be standing again, next time, will you?" The veteran was not amused.

All MPs will have to work harder in their constituencies to impress the party members and activists who decide the reselection. As one MP put it: "Come Wednesday afternoon in a year's time, it'll be dead in the Commons." They'll all be tending their seats. This is a particular worry for ministers. They can't leave London on a Wednesday afternoon; they have government work to do. How will they be able to compete against neighbouring backbenchers with time on their hands?

The reselection process also means that Labour MPs will have to suck up to trade unions. The unions have a large voting bloc in the electoral college that selects parliamentary candidates. So don't expect much bravery between now and 2014 from Labour on strikes, workers' rights or union reform.

It is hard to argue against the equalisation of parliamentary seats. It can't be fair that a voter on the Isle of Wight has roughly a fifth of the voice of a voter in the Western Isles because the constituency has five times the population. As Labour's urban constituencies tend to have lower-than-average numbers of voters, the party wins many more seats than the Tories on any given share of the vote. For Labour to call this equalisation "gerrymandering" is preposterous – the reform makes an unfair system a little fairer.

But there will be arguments about the process, and we shall hear some in the Lords today. There is an unseemly rush to get the new seats redrawn in time for the next election. That means that no local inquiries will be held. And there will be bad feeling when new constituencies cross county borders. Already the Cornish are kicking up a stink about having to share a seat with Devon – though, as David Cameron said of the Tamar, "It's not exactly the Amazon, for heaven's sake!"

But it is the reduction from 650 to less than 600 seats that will make the next couple of years really painful for MPs. No minister has yet produced a convincing reason for it and, since the number of ministers won't be reduced, Parliament will be even more dominated by the payroll vote and even less able to hold the executive to account.

Still, one advantage is that – at last – MPs will be more in touch with the voters they represent. Most of the rest of us have been faced with job cuts and haven't known whether or not we will be laid off. Most of us have been forced to work harder to keep our jobs. So, to those MPs who will be whingeing in a year's time, there'll be only one message from their constituencies: "Welcome to the real world."

m.sieghart@independent.co.uk

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