Manitoba's elections watchdog is investigating whether Eric Robinson, an NDP MLA and the province's aboriginal and northern affairs minister, struck a political deal with a northern First Nations chief, CBC News has learned.

The Progressive Conservatives wrote to Manitoba's Commissioner of Elections, Bill Bowles, earlier this month, asking him to step in after a letter surfaced in 2015 from Opaskwayak Cree Nation (OCN) Chief Michael Constant, accusing

'They're playing cheap political games on the backs of suffering Indians. To me that's unacceptable' - Aboriginal Affairs Minister Eric Robinson

Robinson of promising his band work on Manitoba Hydro's Bipole III project if they supported Premier Greg Selinger.

Constant's letter alleges that Robinson failed to follow through on the contract for his First Nation in exchange for their electoral support.

Robinson denied the deal was ever made and said Constant was motivated by the fact that his bid on the $300-million-plus contract had failed.

Robinson said Thursday, the commissioner's investigation will exonerate him. 

"I'll stand by what I said to you earlier that this is indeed a false accusation," he said. "I think the commissioner will figure that out in quick order."

The Tories say Bowles emailed them on Feb. 7, informing them that their letter has been forwarded to a Winnipeg lawyer to investigate. No timeline for the investigation was given, the PCs said.

"We have laws that would be in place that are in place to prevent this sort of thing," said PC MLA Kelvin Goertzen.

"If it's proven to be true, it's obviously something that's extremely serious and I'm glad that the commissioner of elections is taking it seriously."

The PCs have said the alleged deal came about during a time when Selinger and his supporters, including Robinson, were trying to secure as much support as possible for an NDP leadership election in March 2015.

'Cheap political games,' Robinson says 

Robinson said the PCs are trying to smear him ahead of this spring's provincial election. 

"They're playing cheap political games on the backs of suffering Indians. To me that's unacceptable," Robinson said.

Goertzen said the Tories' concerns have nothing to do with smearing the NDP in advance of the election.

"That benefits everybody to have it looked into and I would hope my opponents on the NDP side would want this to be cleared up too," he said.

Bowles declined to comment on Wednesday. In the past, he has said he does not confirm whether his office receives complaints or whether investigations are underway.

Read the Progressive Conservatives' letter to Commissioner of Elections Bill Bowles:

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With files from the CBC's Chris Glover