Pc Ben Hannam, 22, had also pleaded guilty to possession of a prohibited photograph of a child.
The 17-year-old listed 'areas to attack' including schools, pubs and council buildings.
Being a member of the organisation can lead to 10 years in prison.
Read more on The Huffington Post   The trial comes after counter-terrorism officers carried out a number of raids across
National Action became the first far-right group banned in Britain since WW2
Despite being the first far-right group banned as a terrorist organisation since the Second Would War, neo-Nazi outfit National
'I’m wondering if it was actually real life what I just watched.'
A Fox News anchor has given an impassioned speech against Donald Trump’s latest “disgusting” failure to denounce white supremacists