This could have a "chilling effect" on public engagement with MPs.
Labour MP Trevor Mallard said if a food bank made a complaint to an MP about a constituent who needed a benefit, the details of the food bank and the individual would have to be publicly revealed.
National MP Eric Roy went further: "My concern is that we've created a monster that has a bureacratic imprint that far exceeds the mischief."
Ms Walker believed these unintended consequences could be resolved by a select committee, and said she was open to the bill changing as it progressed.
But she was wary of diluting the legislation to the point that it became ineffective.
She said it was important that there was a transparent regime which informed the public about possible influences on Government policy.
MPs and lobbyists have questioned whether a law change on lobbying was required.
High-profile lobbyist Mark Unsworth said New Zealand was relatively corruption free, and transparency could be improved in simpler ways - such as by strengthening the Official Information Act.
Ms Walker argued that it was important to put safeguards in place now, before New Zealand experienced problems witnessed in Britain and the United States.
Council of Trade Unions boss Helen Kelly supported the sentiment of the bill but was concerned about its wide scope.
"We appreciate what it's trying to do, we don't think it does it and we're worried it will... stop people lobbying freely."
Labour have put up an amendment to have unions and charities exempted from the law change, but Mr Mallard said this was still up for debate. National and Greens did not support this proposal.
Ms Kelly said it was not necessary for unions to be exempted and the bill needed to apply to everyone to be workable.