It is still 12 days to Christmas but Finance Minister Grant Robertson has played Santa early with his announcement that the Government intends to spend $12 billion on infrastructure projects over the next four years.

The timing of the announcement has been seen by cynics as entirely opportunistic, coming as it does just before the start of an election year.

However economists have supported the measure, saying it is time for central government to open its purse strings to help revive an economy that has been faltering and address infrastructure deficits.

There is no doubt that Robertson's package is a huge one. More than half will be spent on transport, primarily roads, with the remainder added to the government's annual spending allowance. The $400m for schools announced at Labour's conference last week is included in the $12 billion figure.

Details of the actual projects will be released early next year but Robertson says many are 'shovel ready.' That could well include roads of national significance left over from the National government.

This package will see the Government increase its agreed maximum projected debt level which was set to be below 20 percent by 2020. That has now been revised to 21 percent by next year.

The investment package comes alongside financial bad news for the Government. The half-year economic and fiscal update is expected to show that a projected $1.5 billion surplus has been revised to a deficit of $900m, with a lower tax take, higher government spending and global headwinds being given as the reasons for the downgrade.

Unsurprisingly National has been quick to use the announcement to portray the Government as economically incompetent, with attack ads appearing on social media within hours.

National leader Simon Bridges says this is a tax and spend government that has turned a financial surplus into a deficit in just two years.

Robertson and the Government will be well aware it is extremely important that they are able to deliver on this major ramp-up in infrastructure investment.

So far the Government's self-proclaimed year of delivery has been disappointing, sprinkled as it was with disasters like KiwiBuild.

That makes Robertson's Christmas package something of a calculated bet as well. The coalition Government has to show it is working before the country goes to the polls later next year.