By Ian Dunt
Senior Liberal Democrats have expressed "shock" and "disgust" at the campaign being run by their coalition partners in the No to AV camp.
With just a few weeks to go until the referendum, Cabinet ministers are becoming concerned that some relations will be hard to repair once the vote is over.
"I am frankly shocked that coalition partners can stoop to a level of campaign that we have not seen in this country before," Chris Huhne said on Newsnight.
"I think it is damaging. There is no doubt about it. I can never remember a campaign that has stooped as low as the No campaign in dredging up stuff that they know is downright lies."
He added: "I think this is the politics of the gutter."
The energy secretary wrote to fellow Cabinet member Sayeeda Warsi earlier this month demanding she stop using "smears" in her campaigning. He has still not received a response, suggesting that their relationship may be irreparable in the wake of the referendum.
Meanwhile, former Lib Dem leader Paddy Ashdown said that attacks on Nick Clegg by the No to AV campaign are "disgusting politics".
No to AV has made full use of Nick Clegg's unpopularity in its campaign, releasing posters with 'president Clegg' emblazoned across them and arguing that AV would make him permanent kingmaker during elections.
But observers were slightly taken aback by comments from David Cameron yesterday, when he insisted that AV would allow politicians to not stand by their manifesto commitments - a comment many took as criticism of the deputy prime minister.
The 'no' camp had the bigger reason to cheer as the most up to date polling figures came out with an ICM survey for the Guardian giving them a 16-point lead.
Fifty-eight per cent of those who had made up their mind and were likely to vote said they would vote no while 42% said they would vote yes.
Twenty-three per cent of respondents remain undecided.