The Manitoba government spent about half a billion dollars less than it had budgeted for infrastructure in 2012, but government officials say there was a good reason for that.

The opposition Progressive Conservatives claims the lower spending was the result of promised major infrastructure projects being cancelled.

Tory MLAs hammered NDP members on the topic during question period on Thursday, demanding they explain what happened to the unspent money.

But Transportation and Infrastructure Minister Steve Ashton said the government spent less than planned in 2012 because it had to deal with severe flooding in 2011.

"So yeah, they can say some projects were deferred. I want to stress again: deferred, not cancelled," Ashton told reporters.

"The reality is there has been a very significant investment on infrastructure over the last number of years, and there's going to be an even greater investment in the upcoming years as well."

According to the Tories, some of the promised infrastructure projects that were cancelled include work on the gates of the Shellmouth Dam, several highway projects near Winnipeg, the construction of three schools in the city, and construction of a hospital in Selkirk.

PC Leader Brian Pallister said he wants to know how the NDP could say infrastructure is a top priority, then spend less money than it budgeted.

Pallister said the NDP's more recent infrastructure promises cannot be trusted.

"They always say that. They're saying it again, but now they're using it as an argument to sell [to] Manitobans that you have to pay a higher PST so we can spend the money," Pallister told reporters.

The government raised the provincial sales tax from seven to eight per cent this past summer.

In its throne speech earlier this week, the NDP insisted that the extra revenue generated by the tax increase will go towards "core infrastructure" such as roads, bridges and flood protection structures.