By Lord Ashcroft

Earlier this week it came to light that a poll I published last November in Sheffield Hallam included a mistake in the data. Concerned that this may not have been an isolated incident, I reviewed two other polls I commissioned from the same company at the same time. As I feared, the mistakes had been repeated.

The data has now been corrected, and the upshot is that in Sheffield Hallam, rather than having a three-point lead Nick Clegg should have been three points behind Labour:

LAB 30%, LDEM 27%, CON 19%, UKIP 13%, GRN 10%.

In Thanet South, rather than a five-point Conservative lead, the poll should have shown a very tight race with UKIP’s Nigel Farage:

CON 33%, UKIP 32%, LAB 26%, LIB DEM 4%, GRN 3%

And in Doncaster North Ed Miliband is a full thirty points clear of his nearest challenger:

LAB 55%, UKIP 25%, CON 13%, LIB DEM 4%, GRN 2%.

The results have been updated on the Constituency Polls section of my website, and the corrected data tables for Hallam, Thanet and Doncaster are also on my site.

I have not been in the habit of naming the polling companies I use, all of which are members of the British Polling Council, and I will not be naming this one. But I cannot allow this episode to cast doubt on the reliability of my polling more generally.

So I must disclose that these three surveys last November are the first and only I have commissioned from a well-known but relatively new polling firm. And no, I won’t be using them again.