A new Ipsos-MORI poll funded by the Unison public service trade union reports that Ken is ahead by 3% on first preferences and 6% after second preferences. (UPDATE: The Guardian report on the poll suggests that the 6% was scaled back to 4% after MORI had factored in whether those interviewed were registered to vote or not.)

The first preference figures are KEN 41%: BORIS 38%: PADDICK 12%. After second preferences are taken into account this become KEN 52%: BORIS 48%

What is not clear is whether the new poll uses the same voting intention question that was adopted in the last MORI survey which attracted some criticism. I have asked the pollster for clarification. An amended version of the question was used in MORI’s only media commissioned poll for the Observer.

The question in the original poll was put in this way: “Q1 In the next election for Mayor of London, the present Mayor, Ken Livingstone is standing for re-election as the Labour Party candidate. Boris Johnson is standing for the Conservatives, and Brian Paddick is standing for the Liberal Democrats, Sian Berry is standing for the Green Party, and there will be other candidates too. In the election for Mayor, voters will have two votes, one for their first choice as Mayor and one for their second choice. If the election were held tomorrow, which candidate would be your first choice?”

The problem here is that Ken was presented in a different way to Boris and that the wording is on the long side.

In the latest Economist doubts are raised about the difficulty of second preference polling by the MD of ICM, Nick Sparrow. He notes that the sample sizes can get very small. In the previous MORI survey the split was down to just 31 people.

This is the first of several polls expected this weekend.

UPDATE: I have now spoken to Ipsos-MORI and have been advised that the question wording was the one used in its Observer poll two weeks ago.

This read: “In the next election for Mayor of London, the present Mayor, Ken Livingstone is standing for re-election as the Labour Party candidate. Boris Johnson is standing for the Conservatives, and Brian Paddick is standing for the Liberal Democrats, and there will be other candidates too. In the election for Mayor, voters will have two votes, one for their first choice as Mayor and one for their second choice. If the election were held tomorrow, which candidate would be your first choice?”

So it was the same as the earlier Unison wording but without reference to the Green candidate.

This is expected to be the last Mayoral survey that MORI will carry out so it is these numbers that it will be judged on. Who would be a pollster?

The immediate impact on the betting markets has been a tightening of the Ken price and an easing of the Boris one.

It is beginning to look as though we might have a line-up of pollsters predicting entirely different outcomes to the election and that the choice for punters will be “which firm do you trust most?” There hasn’t been an election like that in decades.

Historical note: In every single general election and London Mayoral election for the past quarter of a century the most accurate pollster has been the one showing Labour/Ken in the least favourable position. This is what we saw in the 1987, 1992, 1997, 2001, and 2005 general elections as well as in the 2000 and 2004 mayoral elections. Will that hold next Thursday?

SECOND UPDATE: Much of the confusion about the figures has been caused by a leak to the Guardian on which it based its story. The paper put the emphasis on the vote shares BEFORE the non-registered people were taken off.

Mike Smithson