The Labour Party says the Inland Revenue Department has spent $50 million of taxpayers' money scoping out a replacement for its 21-year-old computer system.
Labour says the Government needs to stop burning money on proposals and urgently replace the out-of-date software. It says the system is on its last legs and the Government is just sitting on its hands.
Revenue spokesperson David Clark said on Wednesday the Government needs to lay out a credible timeline for updating the system.
"The minister appears to be sitting on his hands - there's no sense of urgency. Tens of millions of dollars have been spent on international consultants and there is absolutely no tangible benefit to the taxpayer."
Mr Clark said Inland Revenue is preparing a business case at the moment, but won't report back until June 2014.