Last month, Sikorsky International Operations missed another deadline to begin delivering the first batch of 28 CH-148 Cyclones.
MacKay, in Halifax on Tuesday for a shipbuilding announcement, said the federal government is pushing as hard as possible to deliver the choppers.
"This is an example of how procurement can go badly wrong," MacKay told reporters at Irving's Halifax shipyard, referring to the deal struck by the previous Liberal government in 2004. "This is the worst procurement in the history of Canada."
The delivery of the choppers is now four years overdue.
MacKay, who has been defence minister for almost five years, did not take responsibility for the latest delays, instead focussing on the original deal.
"We weren't going to break the contact the way the previous government did and set it back another decade," he told CTV News, referring to the Liberal government's decision in 1993 to scrap a Tory plan to buy a fleet of AgustaWestland EH101 helicopters.
MacKay said there is urgency to get the procurement back on track to replace the nearly half-century old Sea Kings, which have been plagued by technical problems.
"Timelines weren't met. Timelines were broken," said MacKay.
"We have an expectation that they will meet their contractual obligations and if not, there will be consequences. There are financial consequences, and we will pursue those to the full extent."
The first Cyclone was originally due in November 2008, but there have been numerous delays and cost overruns.
When originally proposed 12 years ago, the cost of the procurement was expected to be $2.8 billion.
But that has ballooned to an estimated $5.7 billion, according to a 2010 report by former auditor general Sheila Fraser.
Ottawa has been trying to replace the Sea Kings since the 1980's.
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