The final opinion polls before the election were clearly not as accurate as we would like, and the fact that all the pollsters underestimated the Conservative lead over Labour suggests that the methods that were used should be subject to careful, independent investigation.
The British Polling Council, supported by the Market Research Society, is therefore setting up an independent enquiry to look into the possible causes of this apparent bias, and to make recommendations for future polling.
We are pleased to announce that Professor Patrick Sturgis, who is Professor of Research Methodology and Director of the ESRC National Centre for Research Methods, has agreed to chair the enquiry, and will take the lead in setting its terms of reference. The membership of the enquiry will be announced in due course.
The headline results for the final opinion polls are set out below:
| Con | Lab | Lib Dem | UKIP | Green | Other | Method | Sample Size | Fieldwork | |
|---|---|---|---|---|---|---|---|---|---|
| % | % | % | % | % | % | n | |||
| Opinium | 35 | 34 | 8 | 12 | 6 | 5 | online | 2960 | May 4-5 |
| Survation | 31 | 31 | 10 | 16 | 5 | 7 | online | 4088 | May 4-6 |
| Ipsos MORI | 36 | 35 | 8 | 11 | 5 | 5 | telephone | 1186 | May 5-6 |
| ICM | 34 | 35 | 9 | 11 | 4 | 7 | telephone | 2023 | May 3-6 |
| ComRes | 35 | 34 | 9 | 12 | 4 | 6 | telephone | 2015 | May 3-5 |
| Populus | 33 | 33 | 10 | 14 | 5 | 6 | online | 3917 | May 5-6 |
| YouGov | 34 | 34 | 10 | 12 | 4 | 6 | online | 10307 | May 4-6 |
| Panelbase | 31 | 33 | 8 | 16 | 5 | 7 | online | 3019 | May 4-6 |
| Average | 33.6 | 33.6 | 9 | 13 | 4.8 | 6.1 | |||
| Result | 37.8 | 31.2 | 8.1 | 12.9 | 3.8 | 6.3 | |||
| Difference | -4.2 | 2.4 | 0.9 | 0.1 | 1 | -0.2 | |||