The Australian Workers' Union has thrown its weight behind the idea of a $6 billion pipeline that would take cheap gas from Western Australia to the east coast, even as the concept is being labelled "ridiculously stupid" by one of the country's top energy analysts.

Daniel Walton, national secretary of the union, said a pipeline from the gas fields of WA to South Australia's gas hub of Moomba, as is being pushed by former WA premier Colin Barnett, was "exactly the kind of bold, nation-building project industry super should be backing".