Labour could lose the next General Election following its disastrous poll at the Brent East by-election, former minister Frank Field has warned.
Mr Field says Labour is in 'deep trouble'
He said the party was in "deep trouble" following the Liberal Democrats' Thursday night success in the former Labour stronghold.
But fellow ex-minister Glenda Jackson said she believed Labour could win a third term - if Tony Blair was to quit as prime minister and party leader.
She said the Brent East result showed the electorate had a "complete lack of trust in the government" and therefore in Mr Blair.
Mr Field, a former minister for welfare reform, stressed: "We are in deep trouble and for the first time we see the prospect that we might actually lose the election on a record low turnout."
Ms Jackson, a former junior transport minister, said she had believed Labour would hold on to Brent East with a much reduced majority.
"I am very shocked that it has gone," she told BBC News 24.
"I can only presume the feeling that's running on the streets of Brent is pretty much the feeling that is running on the streets of my constituency and around London generally... and that is a complete lack of trust in the government.
"And of course the government, in the minds of the electorate, is the prime minister."
While voters were also concerned about controversial government plans to introduce foundation hospitals and about the "scandal" of "under-funded" schools, the key issue was the lack of trust in Tony Blair, she said.
"I am already on the record of having called for the prime minister's resignation, specifically on the issue of Dr David Kelly and also where are the weapons of mass destruction that took us to war against Iraq.
"I do not believe that the Labour Party is so bereft of capable, able, talented individuals that we could not select and elect an alternative leader and still win a third term which is what is best for this country."
Ms Jackson said while the forthcoming Labour Party conference would be "beautifully managed", she suspected if there was any kind of dissent it would emerge from the fringe meetings.