Both Mike Smithson and I regularly criticise the BBC’s Daily Politics for commissioning political polls that are not politically weighted. The vast majority of political polls include a voting intention question and (with the exception of MORI, who don’t believe past vote is suitable for weighting in the first place) these are always weighted to be representative politically as well as demographically, normally with reference to how people claim they voted back in 2005.

In contrast, the BBC invariably commission polls without voting intention questions (since their producer guidelines say they need special permission to do so) and these are invariably NOT politically weighted, presumably because past vote weighting requires an extra question and therefore cost more. Does this matter, does it make a difference? Well, for this week’s Daily Politics ComRes asked exactly the same question in their non-politically weighted poll as they did last week in a politically weighted poll for the Indy.

In the ComRes poll for the Independent, which WAS weighted by past vote, Brown & Darling were most trusted by 35%, Cameron & Osborne were most trusted by 33%, Clegg & Cable by 7%.

In the ComRes poll for the BBC’s Daily Politics, which WASN’T weighted by past vote, Brown & Darling were most trusted by 32%, Cameron & Osborne were most trusted by 23%, Clegg & Cable by 4%.

As you can see, while Labour are much the same, there is a huge 10 point difference between the two Conservative scores. It’s possible, of course, that confidence in Cameron & Osborne has massively slumped in the 7 days between the two sets of fieldwork, but this doesn’t seem likely given subsequent national polls haven’t shown this drastic slump. In fact I’m certain it’s because one was politically weighted and one wasn’t. Past vote weighting of phone polls invariably involves making the sample more Conservative and less Labour and the cross-breaks of the ComRes poll for the Indy shows that answers to this question are very closely correlated with voting intention – 72% of Tory voters answer Cameron & Osborne and 80% of Labour voters answer Brown & Darling.

If one believes that political weighting is necessary to get a representative sample for voting intention, then it should also be necessary for other polls where people are asked to compare the political parties or where answers are likely to be aligned to party loyalty.

UPDATE: Andrew Hawkins of ComRes has asked me to link to his comparison a month or two back of a poll he did when political weighting did not make a difference, and I happy to do so here. He has also let me that political weighting made a 2 point difference to the question when it was asked in the Independent (I’m not sure if that is the Conservatives 2 points higher, or the lead 2 points different, or whatever). Presumably recalled past vote was not asked for the BBC version of the question, so we can’t tell how much difference that would have made to the answer.

YouGov’s monthly poll for the Telegraph has topline figures, with changes from the last YouGov poll in the middle of January, of CON 43%(-2), LAB 32%(nc), LDEM 16%(+2).

I’ll do a full report tomorrow when I’ve seen all the figures (I can find references to on the Telegraph website in Jeff Randall’s column, but not the actual report of the poll!), but after a series of polls showing ever larger Conservative leads, this one shows a slight dropping back. One poll like that isn’t necessarily significant, but a couple more in the same vein and it would look like Labour have at least stopped their decline.

The full tables from ICM’s monthly poll are now on their website here. There are two questions that I don’t think were in the Guardian (though I think the first was mentioned in their leader): firstly, there is relatively little appetite for an immediate general election. Only 26% of people would like an election now, 24% later on this year, but 45% say leave it until 2010. As ever with questions like this, the people who most want an election are opposition supporters, but even then only 49% of Tories say they would like one now.

Secondly ICM asked whether Ken Clarke’s return to the front bench makes people more or less likely to vote Conservative. As I’ve said a thousand times before, I really don’t like questions like this, since you get lots of people already voting Tory saying it will make them more likely to do so, and lots of people who don’t vote Tory saying it makes them less so. In this case, it’s probably even less useful since if Clarke does have an positive electoral effect, it will be a vague contribution towards making the Conservative party image more experienced and less posh, rather than thousands of Clarke groupies immediately scampering off to vote Tory on the grounds of his frontbench presence. For the record though, ICM certainly didn’t find any significant Clarke effect on voters – 11% said his return made them more likely to vote Tory, but this was balanced by 10% who said it made them less likely to vote Tory.