The Baird government last week backed down on reforms that would have curtailed the advertising spending of so-called "third party" campaigners to $250,000 at the 2015 election.

Instead, these organisations will continue to be able to spend up to $1.1 million each, dwarfing the $5000 cap on political donations to any party.

The reforms were opposed by Labor and the Shooters and Fishers Party in the upper house, who wanted to protect the ability of unions, and the Sporting Shooters Association, to run noisy political advertising to support their causes next March.

But Liberal upper house MP Catherine Cusack told Parliament it wasn't only unions who effectively donated twice by running scare campaigns.

Ms Cusack recalled a "nasty experience", in which she was approached by Ms Carnell, who made a "disgraceful" and "unsolicited threat".

"It was put to me very bluntly in a conversation that if there was any suggestion that my side of politics would support container deposit legislation her members would be funding a massive campaign against the Liberal and National parties at the 2011 election ... Lion Nathan was prepared to commit $4 million to campaign against us," Ms Cusack said.

Such schemes encourage recycling by consumers, and are supported by environment groups. Cusack was the Liberal's environment spokeswoman at the time. She told Fairfax it was "one of my worst moments in the job".

Ms Carnell told Fairfax Media she represented the Australian Food and Grocery Council at the time, which would never had considered running an election campaign, but the major beverage companies could have.

Coca-Cola and Lion Nathan faced significant costs if the container deposit legislation was introduced, she said.

"I can't remember that discussion, but I could have easily said there's every chance these companies will do what our democratic system allows people to do ... companies who have a particular concern about policy are allowed to run advertising campaigns. It is a strength of democracy," said Ms Carnell, who is now the executive director of Australian Chamber of Commerce and Industry.

The issue of container deposits continues to sit in limbo nationally.

Eleven of the 15 organisations that have registered to run third-party campaigns at the 2015 election are unions.

The unions are expected to run expensive scare advertising against the Baird government on electricity privatisation, and job cuts to teachers and nurses. The Minerals Council is also registered, and may attack the government over its mining and coal seam gas decisions.

Other campaigners include NRMA, the Property Council and the Sporting Shooters Association.