In his letter, Mr English says that while Mr Joyce's Budget plan was "of sufficient quality for Budget 2012" another four-year plan would need to be submitted for next years' Budget.
When that plan was submitted "there are a few areas where improvements could aid Ministerial decision making".
They were:
* Clearer prioritisation of existing programmes relative to any new budget initiatives
* More quantification and discussion of cost pressures
* Greater discusion of how those cost pressures will be met
In a separate document released this morning, Treasury recommended ministers accept a large proportion of submitted four-year Budget plans but also recommended that they agree that the Ministry of Economic Development "be expected to clearly prioritise its activities and programmes in its next four-year budget plan".
Mr Cunliffe said Mr English's letter indicated "serious concerns" about the merger plan.
He claimed due diligence documents dealing with plans for the merged ministry were still being withheld.
"Bill English's letter indicates why: the MBIE business case was not even adequate for Steven Joyce's ministerial colleagues, let alone for the public eye.
"When the merged department starts work next week there will be chaos and that will have flow-on effects in the wider economy."
But Mr English's spokesman said the letter to Mr Joyce was "standard Budget process"
and the Finance Minister "did that with all departments to ensure taxpayers are getting good value for money".
