The campaign for a Yes vote in next month's referendum on electoral reform received a boost today as a new poll suggested that 45 per cent of people intend to support a switch to the alternative vote (AV) system.

The YouGov survey of 2,199 people was conducted after they took part in a "mock AV" election in which they learnt about the workings of the AV system, which allows voters to list candidates in order of preference rather than vote for just one, as is the case under the current first-past-the-post method.

Some 45 per cent said they planned to vote Yes, while 33 per cent opted for No. Another 17 per cent replied "don't know" and 5 per cent would not say.

The findings will help the Yes camp to challenge the No campaign's claim that people are more likely to oppose change the more they know about AV.

A separate YouGov weighted average of the 12 major polls conducted since the turn of the year also gave the Yes camp some grounds for optimism. It put the Yes vote on 36 per cent, the No vote on 31 per cent and the "don't knows" on 29 per cent, while 4 per cent would not say how they would vote.

Nick Pearce, director of the Institute for Public Policy Research think-tank, which commissioned the survey, said: "This poll appears to show that when people engage with AV and are given a chance to try out the system of voting preferences, their support for change grows. It also shows that people can readily understand how AV works and don't find it too complex."

Six in 10 (59 per cent) of people found AV either "fairly" or "very easy" to understand. Some 31 per cent said they would find AV either "very difficult" (13 per cent) or "fairly difficult" (18 per cent) to grasp.