The Lib Dem former leader of Liverpool City Council has urged Nick Clegg to pull out of coalition government.
In a confidential letter seen by the BBC, Warren Bradley urged his party leader to act before "we disappear into the annals of history".
He said Lib Dem councillors were set to lose seats in 5 May's local elections and the coalition was to blame.
A Lib Dem spokesman said being in power brought "difficult decisions", and Mr Bradley's views were not widely held.
Mr Bradley, who led the council for five years, said: "The boil is about to come to a head and burst (probably on election night)."
In the e-mail marked "In Confidence - Private", he writes: "Many other long-serving councillors could be defeated not because of their record, but because of your record and the perception of what we as Liberal Democrats now are."
Mr Bradley, who has previously been critical of the leadership, calls for the end of the coalition: "We have to be independent and we have to sever ties from the coalition; if we fail to do this, we have only our parliamentarians to blame."
But a Lib Dem spokesman responded by saying the letter "simply does not reflect the views of the wider Liberal Democrat membership".
He said: "Moving from a party of protest to a party of power has brought with it some very difficult decisions but we cannot hide from the fact the country is borrowing an extra £400m every single day - the cost of a new primary school every 20 minutes.
"Liberal Democrats are proud to be fighting, as always, on our strong record in local government and now for the first time in 65 years, on delivering in national government."