ComRes have released what they say is their final poll before the European elections on Thursday. Topline figures are CON 20%, LAB 27%, LDEM 7%, UKIP 33%, GRN 6%. The lead for UKIP is far more modest than the eleven points in their weekend poll, but is still pretty robust. The Conservatives remain in third place, the Lib Dems and Greens continue to battle for fourth place. Tabs here.

A lot of the apparent difference between different European polls is down to different treatment of turnout. ComRes have a very stark turnout filter, taking only those people who say they are 10/10 certain to vote. YouGov have a very liberal approach, including everyone who gives a voting intention (though they often tighten it up for final call polls); ICM weight by turnout, the effect of which is sort of a mid-way between the two extremes.

If you look at the tables, we can work out what the polls would have shown using different methods, letting us compare like-to-like. So, if all three pollsters who’ve reported in the last couple of days only took those respondents who said they were 10/10 certain to vote the figures would be:

ComRes – CON 20%, LAB 27%, LDEM 7%, UKIP 33%, GRN 6%

ICM – CON 21%, LAB 30%, LDEM 7%, UKIP 29%, OTH 14%

YouGov – CON 21%, LAB 26%, LDEM 8%, UKIP 29%, GRN 10%

But if all three respondents included the answers of all respondents giving an intention to vote the figures would be:

ComRes – CON 21%, LAB 30%, LDEM 8%, UKIP 27%, GRN 7%

ICM – CON 26%, LAB 29%, LDEM 7%, UKIP 24%, GRN 6%

YouGov – CON 23%, LAB 27%, LDEM 9%, UKIP 26%, GRN 9%

As you can see, it doesn’t explain all the difference (ICM. for example, would have Labour leading even with a strict turnout filter), but it does reduce the contrasts a bit. A softer turnout filter tends to help Labour, a strict one tends to help UKIP.

UPDATE: Two more Westminster voting intention polls tonight – the monthly telephone ComRes poll for the Indy has topline figures of CON 30%(nc), LAB 35%(-1), LDEM 8%(-1), UKIP 14%(+2). The daily YouGov poll for the Sun meanwhile has topline figures of CON 33%, LAB 37%, LDEM 9%, UKIP 11%. YouGov’s Sun poll also asked European voting intention, with topline European figures of CON 21%, LAB 28%, LDEM 10%, UKIP 24%, GRN 12%.