Initial soundings from the regions in the elections for the party's National Executive Committee are said to show that the left is ahead, and confidential memorandums by senior Blair loyalists betray deep concern.
Left-wingers are attracting "tens of thousands of votes" and the Prime Minister's supporters contend that he could end up negotiating party policies with his most implacable political enemies, who would form "an alternative government".
David Blunkett, the Secretary of State for Education and Employment, yesterday made clear his anxiety over the elections, urging Labour members not to return to the internal party strife of the 1980s.
Two private letters to Tom Sawyer, the party's general secretary, from other senior figures in the party, echo his concern.
Ken Jackson, the general secretary of the Amalgamated Engineering and Electrical Union, hints at what his organisation privately believes has been a "monumental cock-up" by the party's headquarters at Millbank.
Mr Jackson's colleagues are furious that voting forms were sent out long before senior Blairite activists were able to dispatch their list of favoured candidates.
In his letter Mr Jackson urges Mr Sawyer to make ordinary party members aware of how crucial the elections are to the future success of Labour.
The union leader points out that most of the press coverage of the election so far has centred on an "extreme left" list of candidates whose sole agenda was opposition. He said it said it would be a disaster if representatives of the Campaign for Labour Party Democracy, Labour Briefing and Tribune - the so-called "grass roots alliance" - were elected.
A letter to Mr Sawyer from Baroness Joyce Gould warns of a return to factional politics. Baroness Gould, former organisation director of the party, expressed her alarm that the NEC could become "an alternative to the Government".
While it was important that the party machinery remained neutral in the poll, she felt it was vital to raise her concerns with the general secretary.
In a statement, Mr Blunkett said Labour needed democratic participation so that the party's policy forums could work in the interests of ordinary men and women. "It is time to put behind us the divisions and the conflict of the past - and with them, those who would attempt to return us to it. We should not return to the days when automatic knee-jerk opposition was seen as a substitute for sensible rational debate in the Labour Party.
"Instead we need a real partnership between the Labour Government, the party leadership and the rank and file."
As loyalists moved to win maximum support for Blairite candidates, fresh feuding broke out between the two wings of the party. Mr Blair was said by a leading left-winger to lack the support of ordinary members.
Liz Davies, a candidate in the elections, said the Prime Minister did not reflect the views of the grassroots. "I don't believe the mood of euphoria that overtook the country 15 months ago when Labour came into power was to celebrate another two years of Tory public spending limits," she told Radio Four's Today programme. In a letter to Mr Sawyer last week the left-winger complained that a new voting system introduced for the NEC elections which allowed members to vote by phone was open to "manipulation and abuse". The party general secretary replied publicly alleging that Ms Davies was guilty of "slur and innuendo" against Labour officials. That sparked the row which gave rise to concerns that the left was gaining too much publicity.
In the elections Blair supporters are backing Sylvia Tudhope, Michael Cashman, Rita Stringfellow, Diana Judah, Terry Thomas and Margaret Payne, while left-wing and non-aligned candidates are Liz Davies, Mark Seddon, Christine Shawcroft, Pete Willsman, Val Price, Andy Howell, Cathy Jamieson, Adrian Daley and Mary Southcott.Reuse content