The union was co-founded by right-wing blogger and National Party pollster David Farrar, along with Hawke's Bay-raised lawyer Jordan Williams.
Mr Williams, who attended Lindisfarne College in Hastings, is a friend of Havelock North political strategist Simon Lusk and featured along with Mr Lusk and Whale Oil blogger Cameron Slater in Nicky Hager's book Dirty Politics.
Mr Nash has said he has taken free advice from Mr Lusk, as he does from a range of people across the political spectrum.
The two men's names were linked again this week with the leaking of a 2012 email from Mr Nash's campaign manager, Rob Johnson, criticising the commissioning of a Lusk report by two of Mr Nash's associates into the possibility of setting up a new political party.
Mr Nash says he did not know about Mr Lusk's report until after it was written and never had any intention of defecting to a new party.
In his foreword for the Monopoly Money report, Mr Nash, who was Labour's revenue spokesman during his previous spell as an MP from 2008 to 2011, said the report's findings showed National had been "delving into the country's coffers to dole out money to their favoured businesses and industries".
"Given that politics is a contest of ideas and vision, any government spending on the scale identified in this report should be transparent and open to public scrutiny. I therefore welcome the Taxpayers' Union's efforts in this area."