Tory backbenchers are playing the Ukip card again.

Certain members of the party have been doing this for a year or so now, sometimes advocating an electoral pact, sometimes endorsing Ukip’s central policy of taking Britain out of the EU, sometimes encouraging the press to think that some of them are even about to defect.

For their latest tactic, they’ve come up with a list of specific seats they believe the Conservatives are set to lose at the election and which Ukip will win, based on the performance of Nigel Farage’s party at the Newark by-election.

The Tories behind this list are members of the Bow Group, and they have coupled their forecast with a call for the coalition to break up sooner rather than later in order for the Conservatives to “articulate their conservative message”.

On the latter point, I happen to think they’re probably right: a dissolution of the coalition ought to take place at least a few months before the election, to enable both the Tories and the Liberal Democrats to regroup and better define themselves ahead of the campaign.

But on their first point, concerning the threat from Ukip, I’m afraid I can’t accept all of what they say. Yes, the Tories could well lose seats as a consequence of some of their supporters switching to Ukip. But for Ukip to actually win those seats, or indeed any seats, is an outcome I’m still not expecting to see.

Why? Three reasons:

1. Ukip has failed to win any of the dozen or so by-elections they’ve contested so far this parliament. When they finally manage to win a seat, I might start to believe they can win some more – or even hold a seat at the general election.

2. The party does not yet have the organisational strength to mount a consistent challenge in a nationwide election.

3. Like it or not, our electoral system remains biased in favour of two-party politics – as the SDP discovered in the 1980s, the Liberals in the 1970s, and Labour way back in the 1910s and 20s.

The Tory seats on the Bow Group’s list of Ukip “gains” are Camborne & Redruth (the Tories’ most marginal seat, and the Lib Dems’ number one target), Thurrock (Labour’s number two target), Newton Abbot (the Lib Dems’ number nine), Waveney (Labour’s no 12), Plymouth Sutton & Devonport (Labour’s no 20) and Halesowen & Rowley Regis (Labour’s number 36).

Both Camborne & Redruth and Newton Abbot were included in Lord Ashcroft’s survey of Tory-Lib Dem marginals last week… and in neither case did the polling show Ukip in the lead.

The list also suggests Ukip are on course to win the following Labour marginal seats: Great Grimsby, Telford, Walsall North, Newcastle-under-Lyme and Plymouth Moorview, along with St Ives from the Lib Dems.

You can consider me flabbergasted if even a single one of these predictions comes to pass next May.

In truth, the Bow Group’s list is just a crude extrapolation of Ukip’s performance in Newark and not a calibrated study of the state of play in each seat.

If you’re going to do a bit of scaremongering, at least try and make it constructive scaremongering.