AS members of the Labour Party await the outcome of its leadership election, a poll has confirmed what most people already suspected – voters deserted the party at the May election because they thought Ed Miliband would not be a good prime minister.

Tory peer Lord Ashcroft based his Project Red Alert on polling and focus groups among loyalists – who voted Labour in 2010 and 2015 – and defectors who switched to other parties. It followed research five years ago to find out why people in the movement thought they had lost in 2010, and what should be done about it.

Ashcroft said they believed then “people had failed to appreciate what Labour had achieved, that swing voters had been influenced by the right-wing media, and although Labour’s policies had been right, they had not been communicated well”.

“Accordingly, they expected the Coalition Government to prove so dreadful that people would soon see the error of their ways – Labour would not need to make any big changes in order to win the following election,” he said. “The question for the new leader, whose identity we will know on Saturday, is not just how the party can start winning again, but whether Labour as we know it will survive.”

Ashcroft said he examined the views of Labour loyalists and defectors and found that few in the former group had voted with any enthusiasm.

The majority of all defectors said Miliband had helped push them to another party. Those who joined the Tories were more likely to say they had been put off by the impression that Labour were not ready to form a competent government. This group was also more likely to say they struggled with their decision: nearly a fifth said they found it “very difficult indeed”.