The backbench MP Rhodri Morgan yesterday rejected pleas to drop out of the race with Alun Michael, the new Welsh secretary, for the top Labour job in the new assembly.
An emergency meeting of the executive in Cardiff yesterday decided to postpone making a decision on the party's means of choosing a leader.
The executive, which was lobbied by noisy protests from members who fear Millbank will impose Mr Michael as sole candidate, will meet again later this week to make its final recommendations.
As the London Labour party prepared to meet today to determine its selection procedure for the post, the Tories made clear that the millionaire novelist would not be barred.
Mr Livingstone said last night that he could not believe reports that the party was preparing to sideline him in the race to become the capital's first directly elected mayor.
'I'm convinced that this is just briefing by the same over-zealous, young party officials who are claiming they don't want a contest in Wales and have blocked sitting MEPs,' he said.
'Tony Blair has made clear his backing for one member, one vote and it would be very damaging for him to drop that commitment.
The board of the London Labour party, which is today expected to back a panel that could rule out the Brent East MP will pass on its decision to the organisational committee of the NEC later this month. The NEC will then make a ruling in January on whether it will allow a 'stop Ken' device.
Geoff Martin, London convenor of Unison - which is backing Mr Livingstone - said it was 'outrageous' that a 'trap door' was being considered to remove the MP.