Tim Pendry, who has attacked the Labour hierarchy as "Leninist", is now expected to become a victim of the "control freakery" he condemned. Party officials plan to take disciplinary action against him for seeking to foment a rebellion that could harm Labour's electoral prospects.
Mr Pendry has resigned as chairman of his local Labour party branch in Islington, north London, to protest at the way national party bosses chose the candidates for the June European parliament elections.
He accused Labour leaders of "crude manipulation" of the closed list system, under which people will vote only for a party rather than individual candidates, to ban critics of the Government from standing.
"In view of the associated, crude and systematic stifling by the party bureaucracy of constructive dissent within the party, I have decided not to donate funds, canvass or engage in any electoral support activity, or even vote in the European election," said Mr Pendry.
In a letter to party bosses, he said he would urge other members who asked his advice to abstain from party activity during elections. "If I had wanted to join a communist party with a Leninist approach to candidate selection, I would have done so," he said.
Mr Pendry is also standing down as co-ordinator of the Grassroots Alliance, a centre-left group that scored a victory over Blairite candidates in last year's elections to the party's National Executive Committee.
A Labour spokesman said the party was "actively examining" taking disciplinary action against Mr Pendry over his call for a boycott of the campaign - a move that could result in his expulsion. "It is pretty clear cut; this is something we take very seriously," said the spokesman.
Mr Blair's allies claimed Mr Pendry's decision to quit his post with the grassroots group showed that what they called "the ragbag alliance" was in trouble.
Last night Mr Pendry said his departure from the group was "completely unrelated" to his decision on the European elections. He was relaxed about facing disciplinary action. "My view is that the Labour Party is run by a small clique, a machine. It does not have any more to say to most of the people it serves," he said. "So let them do their worst; I am not breaking from the party. It may break from me."
The call for an activists' boycott will worry Labour officials, who already fear it will be hard to motivate traditional Labour supporters to turn out in the European poll and in next month's local authority elections.
In another protest, Lynne Armstrong, a prospective Labour candidate in the European elections, has withdrawn from the party's list in the South- east region because she feels she can no longer represent New Labour.
She has opposed a pounds 2,000 levy imposed on constituency Labour parties to raise funds for the Euro campaign, and told the left-wing Tribune newspaper it was wrong "to rip off people who do not have the money".