Ms Coddington refrains from using the terms left and right wing, saying these have become almost devoid of meaning.
Referring instead to pro-interventionist and pro-market standpoints, she accuses National Radio of failing to cater for the 37 per cent of New Zealanders who voted for parties with the latter policies.
She explains pro-interventionist as "the collectivist or socialist belief in the forceful manipulation of economic affairs" and pro-market as an economic and moral view that governments should intervene only minimally in economic activities.
Her report is backed by a preface by former Radio New Zealand directors John Isles and Denis Dutton, who declare a long-standing "nagging" concern about the underlying intellectual framework of some programmes.
Radio New Zealand chairman Brian Corban is on record attacking his predecessors for allegedly wanting to privatise its news service and "rip the guts" out of public-service broadcasting.
Last night new chief executive Peter Cavanagh said he could not comment in detail as Ms Coddington had not consulted Radio New Zealand, but independent research showed that more than 80 per cent of its audience believed it provided fair and balanced information.
Ms Coddington says in her report she has no problem with radio presenters having certain views as long as they declare these on air.
But she says National Radio does not have a single presenter who clearly and publicly holds a pro-market philosophical framework.
She attacks its range of guest commentators, from Auckland financial planner Murray Weatherston to various overseas broadcasters and consumer issues specialists Bill Bevan and Stephen Price as showing a "disquieting homogeneity" and lack of diversity.
Mr Weatherston expressed surprise to the Herald at appearing at the top of her hit list, saying he believed he leaned more to a pro-market than pro-interventionist viewpoint, "although some of my friends would probably accuse me of having a social conscience".
Ms Coddington also trawled National Radio news bulletins for a week in September to analyse the selection and treatment of "perspectives within news stories".
She concluded that 48 per cent of perspectives were those of pro-interventionist new sources, against 27 per cent pro-market.
She accused the state broadcaster of airing the views of more pro-interventionist groups such as unions in education stories than those of pro-market lobbyists such as private school representatives.
And she said it was more likely to broadcast an opposing viewpoint after an item from a pro-market group, while leaving claims by pro-interventionists uncontested.
She also clobbered National Radio's business news for concentrating too much on on corporate announcements and having lent its microphone to just one business organisation representative - the Auckland Chamber of Commerce - in a nine-day survey period.
News 'perspectives'
Radio New Zealand
Pro-market - 27 per cent
Neutral - 26 per cent
Pro-interventionist - 48 per cent
New Zealand Herald
Pro-market - 32 per cent
Neutral - 32 per cent
Pro-interventionist - 36 per cent
Newstalk ZB
Pro-market - 33 per cent
Neutral - 26 per cent
Pro-interventionist - 41 per cent
Source:
Saving Public Radio report