Nick Clegg is "toxic" on the doorstep, according to a senior Liberal Democrat peer.
Lord Storey, the party's education spokesman, said the deputy prime minister is "not a popular person" among voters in his home city of Liverpool.
The peer stressed he found it "very difficult" as Clegg is a "nice guy" with principles who passionately believes in what he is doing.
Does he look toxic to you?
The comments will heap further pressure on the Lib Dem leader who has faced disastrous local and European election results as well as a bid to undermine his leadership from peer Lord Oakeshott.
Lord Storey also admitted the party had not just lost councillors in last month's local elections but entire political machines including fundraisers and organisers.
He told BBC One's Sunday Politics: "Knocking on doors in Liverpool, I have to tell you that Nick Clegg is not a popular person.
Lord Storey softened his remarks by saying Clegg was 'a nice guy'
"And some might use the word toxic.
"I find this very, very difficult because I know Nick very well and I see a principled person who passionately believes in what he's doing, and he's a nice guy."
He went on: "In parts of the country, take Liverpool as an example, where we had 60 plus councillors, we're down to three.
"It's not just the councillors you lose, you lose all the political infrastructure.
"So you lose the deliverers, and the fundraisers and the organisers and the members of course.
"All that will have to be rebuilt."
Meanwhile, former Lib Dem leader Sir Menzies Campbell insisted Clegg is still the best person to lead the party but stressed the need for colleagues to be more assertive about taking the credit for coalition policies put forward by the junior partners.
He said the party now needed to rebuild itself "from the bottom up".
Sir Menzies told the programme: "Nick Clegg is a man of principle, he's a man of enormous resilience, if you consider what he's had to put up with, my view is quite clearly that he is the person best qualified to lead the party between now and the general election, through the election campaign, and beyond."
"I think you'll find we're going to be rather more assertive about taking the credit. We will do everything in power to change (public opinion) between now and May 2015."