The man appearing on television screens across the country promoting the Abbott government's Intergenerational Report - science broadcaster Karl Kruszelnicki - has hardened his stance against the document, describing it as "flawed" and admitting to concerns that it was "fiddled with" by the government.

Dr Kruszelnicki, widely known as Dr Karl, has previously revealed that he had not read the full report before he agreed to front the taxpayer-funded campaign, which is expected to cost millions.

Dr Karl Kruszelnicki in the Intergenerational Report advertisement. Credit:challengeofchange.gov.au

The Intergenerational Report - a snapshot of Australia's economy and society in 40 years - was criticised by Labor as a "highly political document" for, among other things, downgrading climate change from its own chapter in 2010 to three-and-a-half pages in 2015.

"As far as I can see, it's a flawed report," Dr Kruszelnicki told Fairfax Media.