The group running under the banner of "Members First" were also claiming last night they had the support of Cabinet heavyweights Robin Cook, the Foreign Secretary, David Blunkett, the Education Secretary, and Frank Dobson, the Health Secretary.
Ms Jackson's demonstrated backing for the group, by chairing a press conference in London attended by the six candidates, follows reports that the leadership is "in panic" over fears that the left-wing Grassroots Alliance is better organised and will win more seats.
The group, which includes the actor and gay rights activist Michael Cashman, will mount a counter-attack in the increasingly vitriolic battle for the six seats on the NEC for constituency members.
This led last week to an attack on Liz Davies, a left-wing candidate, by the party general secretary, Tom Sawyer over the conduct of the telephone ballot.
Mr Blair's cabinet colleagues have warned the leadership to avoid having its fingerprints on the campaign by Members First to stop the left- wing slate.
The former Oscar-winning actress, who is expected to run for the position of Mayor of London next year, is seen as a staunch support of Tony Blair's modernisation of the party. Her support for the group will be seen by the left as confirmation that Members First are being put up by the leadership to stop the left candidates. That was denied last night by the group's press officer, Phil Jones.
"Glenda Jackson is going to talk about the people who are in the party who support these candidates. She is going to say Robin Cook, David Blunkett and Frank Dobson will be supporting them," said Mr Jones.
"The main reason for the press conference is to give the press an opportunity to show these people are not a bunch of Blairite clones. These are not people who are on-message the whole time.
"We have no problem with people saying these are people that Tony Blair would rather have than Liz Davies. I think the difference is between people who believe that on the whole the Government is doing a good job, and those on the hard left who want to undermine the leadership, who never wanted Blair as the leader and don't want him as Prime Minister."
Mr Jones, the researcher for Ben Bradshaw, the gay Labour MP, said Members First was set up at the instigation of a Labour supporter, who has been given a peerage by Mr Blair, to implement the "party into power" strategy paper endorsed by the annual conference last year.
"I don't think it is anything to do with left versus right at all. It is completely crazy for the Grassroots Alliance to claim they are a centre- left grouping with representatives of the Hattersleyite right-wing and that we are just right-wing. Michael Cashman is not right-wing."
The candidates on the Members First slate with Mr Cashman are: Diana Jeuda, Rita Stringfellow, Terry Thomas, Margaret Payne and Sylvia Tudhope. Several have strong trade union links.
Steve Richards, Review, page 4