Party heavyweights clash over referendum arguments
Senior politicians - including two former party leaders - have clashed over whether changing the way MPs are elected will make the process fairer.
Labour MP Tessa Jowell told a special referendum edition of the BBC's Daily Politics that a new system would make politicians "behave differently".
Ex-Lib Dem leader Charles Kennedy said the current process was "corrupting".
But former Conservative leader Lord Howard said the proposed change would produce "perverse" results.
In the first UK-wide referendum for 35 years, voters will be asked on 5 May whether they want to replace the current first-past-the-post system for Westminster elections with the alternative vote.
Under the current system, voters select one candidate and the individual with the most votes wins while under the alternative vote, people can rank candidates in order of preference.
Labour's former deputy leader, Lord Prescott, also took part in the special debate to be broadcast on BBC Two on Wednesday at 1200 BST.
The four political heavyweights debated which of the two systems was fairer, which would make MPs and Parliament more accountable and which would lead to a better standard of politician.
Shadow Cabinet minister Tessa Jowell said the alternative vote was not a "cure-all" to the problems facing the political system but was a "small step" in the right direction.
"It forces us to be better politicians, reaching out beyond what might be defined as a core vote," she said.
"That will produce a better form of politics."
Labour is split over the issue of electoral change with party leader Ed Miliband among those backing a switch to AV, while Lord Prescott and other senior figures oppose it.
Ms Jowell said it was "nonsense" to suggest that AV would result in more hung Parliaments than the current system, quoting research suggesting that no other elections, apart from the 2010 poll, would have resulted in coalition governments under AV since the late 1970s.
"Majority governments are just as possible under AV as they are under first-past-the-post."
But former Labour deputy prime minister Lord Prescott said AV would "inevitably" produce more coalition governments.
"More to the point, it does not deliver the promises you made to the electorate. It is fixed by a few people in the room as you have seen with Nick Clegg and David Cameron."
Mr Kennedy, whose party backs a switch to AV, said it was not simply a stepping stone to another system in the future but "a decisive step forward to reforming politics".
He said: "This is not a Trojan horse for a more proportional voting system. It is categorically not."
He added: "We have got an ossified, out-of-date, corrupting form of elections called first-past-the-post and we have got an option for a degree of moderate reform. People should seize that."
Lord Howard, whose party backs the current system, said adopting alternative vote would make little or no difference to at least half of current parliamentary seats and that more than four in ten of MPs would still be elected without the backing of 50% of their constituents.
"Here in Britain, we have a clear, decisive and effective system," he said.
"It is the most widely used system in the world and it is based on a simple principle - everyone should have a vote of equal value."
The Daily Politics' Referendum Debate will be broadcast on BBC Two on 6 April from 1200 BST.