(Adds details on previous layoffs)
CALGARY, Alberta, March 22 (Reuters) - Canada's Enbridge Inc said on Wednesday it would cut about 1,000 positions, or 6 percent of its work force, after buying Spectra Energy Corp of Houston, the first layoffs for the combined energy infrastructure company, the biggest in North America.
The takeover announced last year, the most significant energy deal since oil and natural gas prices crashed in mid-2014, had highlighted how pipeline companies were under pressure to merge as they grappled with overcapacity and sliding tariffs that had slowed dividend growth and unnerved investors.
It is relatively common for layoffs to occur in mergers, and even without such deals oil and gas companies have been shedding staff in a bid to cut costs.
At the time, an expert said the deal had no serious antitrust problems as the companies' networks have limited overlap.
But duplications exist in the combined company's "organizational structure," Enbridge spokesman Todd Nogier said.
"After a careful evaluation, Enbridge has taken the difficult but necessary step to address the overlap."
Nogier said the workforce reductions are a component of the "synergies" expected over the coming months as it fully integrates the companies. The company declined to disclose details on the positions that will be cut.
Last year, Enbridge cut 530 people, or 5 percent of its work force, after what it said was an organizational review. The layoffs happened after the merger was announced, but before it took place and were unrelated, according to the company.
Those layoffs followed the loss of another 500 positions in 2015.
Tens of thousands of jobs have been lost in both the Canadian and U.S. oil and gas sector since energy prices crashed. (Reporting by Ethan Lou in Calgary, Alberta; Editing by Marguerita Choy and Grant McCool)