David Cameron and Nick Clegg have traded blows over electoral reform as the referendum battle began in earnest.
The Prime Minister warned that introducing the alternative vote system would be “a massive backward step for accountability and trust in our politics”.
But his Liberal Democrat deputy, speaking in Leeds, insisted it was the only way to tackle corruption at Westminster and prevent millions of voters being “ignored”.
The coalition allies used speeches delivered hours apart to fire their first salvoes in the campaign.
Both men stressed that the result of the ballot on May 5 was not make-or-break for the Government.
However, there were early signs of the potential tensions when Mr Cameron took Mr Clegg to task for supporting AV after previously branding it a “miserable little compromise”.
Despite senior Tories and Lib Dems extolling the virtues of coalition over the past nine months, the Premier also expressed concern that hung parliaments would become “commonplace”.
“It won’t surprise you to hear me say that is not necessarily a bad thing and that, as happened last May, it can bring parties together in the national interest,” he told an audience in central London.
“But let’s be clear, when there are more hung parliaments there will be more haggling and horse-trading between politicians – both before and after elections.
“There will be gamesmanship between parties in different constituencies as they try to stitch up second preference votes.
“And there could well be an occasion where we have a genuine second-choice government.
“If the last election was under AV, there would be the chance, right now, that Gordon – Brown would still be prime minister.”
He said although first past the post had not delivered a decisive verdict at the last election “in terms of who won”, it was “decisive in terms of who lost”.
“I think any system that keeps dead governments living on life support is a massive backward step for accountability and trust in our politics,” Mr Cameron added.
Speaking in Leeds earlier, Mr Clegg blamed the existing voting system for encouraging politicians to abuse expenses. For years, politicians and parties have courted the votes of a few thousand people in marginal seats and ignored the rest.”
“It is because there are so many MPs with jobs for life that there are so many who can take their constituents for granted.
“And it is because there were so many MPs taking their constituents for granted that so many abused their expenses.
“There was a clear link between how safe an MP’s seat was and how likely they were to abuse the system.
“When a person is corrupt, they should be punished.
“When a system makes corruption more likely, it should be changed.”
He urged the public to “remember how it felt when you heard about MPs spending your money on duck houses and having their moat cleaned”, insisting: “We deserve something different.”
While the first-past-the-post system was outdated, AV would make MPs “work harder”, according to Mr Clegg.
“It means that parties will have to compete for votes in every corner of the country and not just those few marginal seats,” he said.
“It means more people get listened to and more respect for the different opinions and feelings we share as a nation.”
Mr Clegg dismissed objections that AV was too complicated, pointing out that the system of ranking candidates by preference was already used in Australia and the London mayoral elections.