The wording of the question in next year's referendum on changing the Westminster voting system is confusing to some voters and should be rewritten, a watchdog said today.
Research by the Electoral Commission - which is required by law to assess the question - found people "with lower levels of education or literacy" found it "hard work" or incomprehensible.
"The structure of the question, its length, and some of the language used made it harder to read than it needed to be," the Commission concluded.
A public vote on moving from the first past the post system to the alternative vote (AV) is planned for May 5 next year.
Under legislation being debated by MPs, the question put to the electorate would read: "Do you want the United Kingdom to adopt the 'alternative vote' system instead of the current 'first past the post' system for electing Members of Parliament to the House of Commons?"
Instead, the commission suggested, the electorate should be asked: "At present, the UK uses the 'first past the post' system to elect MPs to the House of Commons. Should the 'alternative vote' system be used instead?".
The Commission also found a significant lack of awareness of how the existing system worked and even less understanding of what AV would involve - although it noted that the pro-and anti-AV campaigns would bolster public knowledge in the run-up to the vote.
Jenny Watson, chairwoman of the Electoral Commission, said: "We have an important role to play in providing an independent check that voters find the referendum question easy to understand and the best way to do this is to ask the public themselves.
"People told us that the wording of the question - with some changes - was easy to understand.
"However, they have a limited knowledge of what the 'first past the post' system is and almost no understanding of the 'alternative vote' system.
"Our research took place without the campaigns and extensive media coverage that will be in place in the run up to the referendum.
"We found that when participants had more information on how both systems worked, their understanding improved and they could cast their vote in the way they intended."
She went on: "Campaign groups and the media will play an important role in the run up to the referendum. And the Electoral Commission will also be playing its part, by providing every household in the UK with information on both voting systems and how they can cast their vote."
The campaign will pit the Conservative and Liberal Democrat coalition partners publicly against each other, with David Cameron firmly opposed to the change.
Pro-AV campaigners were pleased this week when new Labour leader Ed Miliband confirmed he would personally back a "yes" vote.
But it remains unclear whether he will impose the party whip on Labour MPs to help ensure the legislation enabling the referendum is not blocked in Parliament.
Previously the party was opposed to moves to tie the vote to a reduction in the number of constituencies to 600 and redrawing boundaries to make them more equally-sized.
The Opposition claimed it amounted to gerrymandering in favour of the Tories.
There is also dissent on the Tory backbenches over the planned date of the referendum - which coincides with elections to Scottish and Welsh devolved administrations and some English councils.
Rebels say that will confuse voters and skew the result.
A Cabinet Office spokeswoman said: "We welcome the report and will consider its suggestions carefully."
The Commission's findings were welcomed by Matthew Elliott, campaign director of the NO2AV campaign, which had raised similar concerns.
"It is vital that the British public understand the important decision they have to make and we hope that Parliament and the Cabinet Office take note of the Electoral Commission's findings when drafting the eventual question," he said.Reuse content