Key Points:

John Key will announce a range of roading, state housing and school upgrades worth about $500 million. They will be projects that can be started almost immediately.

The $48 million Kopu Bridge replacement was scheduled to start in 2011 but has been brought forward to July this year.

Work on the 480m bridge is estimated to take two and a half years.

Four other big roading projects will be named in the package: two in Hawkes Bay, one in Wellington and one in Christchurch. The 94km Waikato Expressway from Mercer to south of Cambridge is not part of the package and will be among the very large infrastructure projects the Government will consider for fast-tracking.

The projects are expected to soak up some of the skilled tradesmen in the building and construction sector which has been hard hit by the recession.

Mr Key will confirm an insulation programme for state houses.

He said on Monday that expanding it to private sector housing was a later possibility. Upgrades of some school properties that have already received planning consent will also be included.

In another aspect of its stimulus package, National last night introduced the tax bill comprising relief on provisional tax rules announced last week to relieve small and medium businesses.

Labour leader Phil Goff said about three-quarters of the Government's stimulus package that Mr Key was bragging about had been in Labour's 2008 Budget or in its tax bill.

Progressive leader Jim Anderton criticised the size of the relief package to small and medium businesses ($480 million over four years) amounting to $10.50 a week, "which would hardly buy a big packet of peanuts at the supermarket".

Mr Key warned against MPs calling for more spending.

Excessive debt could also bring a downgrade from credit agencies which would lead to higher interest rates and lower growth.