That provided the platform for him to warn the likes of New Zealand Oil and Gas and other companies and individuals who had a stake in Pike River Coal before the firm went into receivership to stump up with the cash even though technically they are not liable.
Not only had Cunliffe gained the political initiative over National, he noted the governing party's reluctance to take a similar line to Labour and instead look for reasons (or excuses) not to force the payment of compensation.
He sought to portray that reluctance as another example of how John Key's five-year-old administration has lost its "moral compass" and is only interested in doing things which help National's big business mates who fund that party.
Labour this week levelled similar accusations of loss of moral compass at Key and Foreign Minister Murray McCully for sacrificing New Zealand's proud record of upholding human rights so that they could digest canapes and quaff champagne at last weekend's Commonwealth summit and cuddle up to the repugnant Sri Lankan government and be rewarded for their softly-softly diplomacy with the donation of an elephant for Auckland's zoo,
Do Labour's claims really stack up in both cases? With regard to Sri Lanka, much was made of the decision by Canadian Prime Minister Stephen Harper to boycott the summit because of what he said were ongoing reports of intimidation, incarceration, disappearances and killings of Tamils in the country's north and the Sri Lankan government's failure to uphold the Commonwealth's core values which were "cherished" by Canadians.
Key came under pressure to follow suit. Yet in Canada, there was much suspicion that Harper had opted not to go to avoid upsetting the local Tamil community. Around 300,000 Tamils of largely Sri Lankan origin live in Canada. Tamils make up as much as 7 per cent of the population of Toronto. Their votes are seen as capable of swinging the outcome in marginal seats at election time.
Harper has also come under fire for preferring isolation of a regime that fails to meet acceptable democratic or human rights standards rather than engagement with such a government.
Under McCully's watch, New Zealand's foreign policy has shown a preference for engagement, especially with regimes, such as the one in Burma, which have accepted some degree of political reform is necessary in order to lift economic performance and trade with neighbouring countries.
Engagement offers the possibility of influencing things, isolation only allows for ineffectual grandstanding by the party doing the isolating.
Cunliffe has said that had he been in Key's shoes, he would have gone to Colombo - but only to ensure a country other than Sri Lanka was installed as chair until the next summit in two years' time.
Unfortunately for Cunliffe, the Commonwealth - a sluggish beast at the best of times - possesses neither the mechanism nor the inclination to both punish and embarrass its host in such a manner.
As for New Zealand's stance, McCully revealed in Parliament this week that it was not as soft as many had assumed. It supported some form of war crimes inquiry as mooted by Britain's Prime Minister David Cameron. New Zealand believed those responsible for the deaths of thousands in the north should be held to account, just as there should also be a process for achieving reconciliation in the aftermath of the civil war, along with some form of devolution in the north.
As for Pike River, the claim that National has been heartless has to be set against the $5 million that ACC will have paid to the miners' families by the end of next year. As well, the Government is also forking out some $7 million on a mine re-entry operation to try to recover the miners' bodies.
National has tried to get Cunliffe to explain why he thinks a death in one particular workplace should be treated in a far more favourable financial light than a death in another.
This is important because Labour has been pushing for an inquiry into safety in the forestry industry, a sector which has suffered a high number of workplace deaths in the past year.
Labour cannot afford to be seen to be assessing the mining and forestry sectors according to different criteria.
National also wants Cunliffe to explain how a precedent-setting, lump-sum compensation payment would square with ACC's ban on going to court to sue for damages.
In fact, there is already a precedent. Some $2.7 million was paid out by the Government in 1997 to settle claims arising from the Cave Creek platform collapse.
Despite that, Cunliffe has deliberately and wisely avoided swallowing the bait and getting into an argument where he might well end up on the losing side.
The strongest sign he is winning came in a cartoon in Wellington's Dominion-Post newspaper this week. It portrayed the Government as a crocodile shedding tears while chewing up a document entitled "Pike River Families Compo". That said it all. Well, not quite. It is hard to envisage Key tolerating taunts from Cunliffe regarding Pike River from here until election day. Time perhaps for some prime ministerial pragmatism over principle?
