A gaping hole in the country's tax take should be concerning the Government as it may affect New Zealand's future credit ratings, Labour revenue spokesman David Clark says.
He also warned that a lower tax take would eventually affect the services the Government funded, such as health and education.
Possible school cuts had already been signalled in Dunedin.
The Government accounts released last week showed core Crown tax revenue had been nearly 3% lower in the seven months ended January than forecast in the pre-election fiscal update provided by Treasury in October, just before the election.
However, the actual tax take for the January 2012 period was 4.8% ahead of the January 2011 figures.
But the figures that should be closely monitored were included in the "Briefing to the Incoming Minister" (BIM) released in February, Dr Clark said.
There, the Inland Revenue Department noted a drop in the tax take from 35% of GDP to 31% during National's first term of government.
IRD estimated about 2.5% of the 4% decline was attributable to Government policy changes, and the remaining 1.5% attributable to the global financial crisis, he said.
"The Government continues to push the line that its 2010 tax switch was 'broadly revenue-neutral'. Entertaining the word broadly in this context is stretching the English language beyond belief," Dr Clark said.
Blaming the widening deficit on the Canterbury earthquakes or the global financial crisis was no longer a credible excuse for the $12 billion deficit, he said.
Asked if companies had reported lower profits because of the global financial crisis and the lower tax take as a percentage of GDP was a blip, he said IRD had allowed for a 1.5% drop. The rest of the fall was down to Government policy changes.
If the Government believed the tax take would improve over time, it needed to demonstrate that to the public, he said.
"National members continue to repeat as an article of faith that the economy will improve with time, but the reality is they have no idea how they are going to achieve this."
Labour's plan to push investment towards the productive sector through the use of a capital gains tax on speculative investment was something the Government was not willing to consider, Dr Clark said.
