Threatening to pull your party's support from the Government is not something you do lightly. For credibility's sake, it is a threat you can only make very occasionally.
So yesterday's blunt warning to National from Tariana Turia - someone not prone to bluster and empty gestures - is an indication matters are fairly serious.
The Maori Party's unhappiness centres on the longstanding clause in the State Owned Enterprises Act which states the Crown should not act in a manner that is inconsistent with the principles of the Treaty of Waitangi.
National wants to ditch the clause in forthcoming legislation necessary to allow the Government to take some state companies out of the ambit of the SOE Act in readiness for partial privatisation.
National argues such an umbrella clause is unsuitable for part-privatised state corporations as it cannot bind private sector shareholders.
The Maori Party points out that these companies will retain a minimum 51 per cent Crown shareholding and that National's stance shows deep down it does not really take the Treaty seriously.
The Prime Minister said a solution would be found to ensure the affected corporations met their Treaty obligations. However, there was enough concern in the Beehive about the threat for Finance Minister Bill English to hastily convene a peacemaking meeting yesterday with Turia and Pita Sharples, the Maori Party co-leaders.
What is not in question is that National's handling of the matter has been less than tidy. In its haste to get partial share floats in the likes of Mighty River Power under way, it has either ignored, overlooked or simply forgotten the huge significance of the clause to Maoridom.
The interpretation of that clause by the Court of Appeal in a 1987 case taken by the Maori Council effectively inserted Treaty into New Zealand's unwritten constitution and has since set the benchmark for the "partnership" between the Crown and Maori. Its sudden absence from National's "mixed ownership model" is simply unacceptable to Maori.
The Mana Party's Annette Sykes may be exaggerating in saying the clause's removal is "the foreshore and seabed of 2012". But she is not exaggerating by very much.
As Sykes also stressed, the Maori Party might as well surrender any notion of being an independent voice. However, the Maori Party was already unhappy with ministers rubber-stamping the Crafar farms sale to foreign interests. It is now questioning why National has chosen to be so provocative so close to Waitangi Day.
National's motives may be more basic. The more conditions and encumbrances surrounding the share floats, the less the Government can expect to reap.
National may also have been lulled by the Maori Party's ambiguous stance on asset sales. While opposing the share floats, the latter party wants iwi to have a major slice of the action.
National might have thought it could buy Maori off. If so, it has misjudged the Maori Party and the political pressures now raining down on Turia and Sharples. In the last term, the Maori Party portrayed itself as the innocent bystander to National's actions even as it helped prop up the minority Government. Its opponents are not going to allow the Maori Party that luxury this term. The fuss over the Treaty clause shows just how acutely Turia and Sharples are aware of that.