MONTREAL -- One of Canada's largest media unions is sounding the alarm over Bell's $3.4-billion deal to buy Montreal's Astral Media, which would add to the telecom company's extensive radio and television business.

The CRTC is in its third day of hearings into whether the telecom giant (TSX:BCE) should be allowed to forge a deal that would make it even larger.

Bell's parent BCE Inc. already owns the CTV television network and former Chum radio group as well as their extensive list of specialty television channels and Bell Canada, the country's largest telecom company.

The Communications, Energy and Paperworkers Union of Canada told the federal regulator on Wednesday that media concentration in Canada has had troubling consequences.

"Apart from chilling diversity and neutering competition, concentrated media ownership has reduced employment opportunities in content creation," said union vice-president Peter Murdoch.

"This is why CEP opposes this application."

He added that if the CRTC does approve the deal it should ensure that Bell strengthens original, local broadcast news.

"You could approve it, however, if the evidence presented to you establishes that it will clearly, significantly and unequivocally benefit Canadians and the broadcasting system, and if its benefits offset the extremely serious concerns it has raised -- especially for news and particularly local news."

Murdoch says the CRTC should require Bell to spend $43.5 million on radio and TV news production.

The union also says that since 2008, CTV has cut its TV staff by 24 per cent, including 233 people since BCE acquired CTV in 2000. Astral has cut its radio news spending by eight per cent since 2008, Murdoch added.

Rogers says it is opposed to the deal unless the CRTC forces Bell to get rid of Astral's English specialty channels, such as The Movie Network, HBO Canada, Family Channel.

"It can order Bell to divest of Astral's English-language television services as a condition of approval of this acquisition," said Pam Dinsmore, vice-president of regulatory affairs at Rogers.

Like BCE, Rogers has extensive media and telecom businesses that compete in several major markets, particularly in Ontario, Alberta and British Columbia.

"If Bell is allowed to own both CTV and Astral, it will have overwhelming control over television on all screens in Canada," said Dinsmore, referring to TVs, computers, smartphones and tablets.

"Those consumers who subscribe to one of Bell's TV competitors will either be unable to access content from CTV and Astral, or they will be forced to pay significantly more for it."

A few years ago, Rogers was able to acquire several Citytv conventional television stations -- including its flagship station in Toronto -- that BCE had wanted when it bought Chum Ltd. several years ago. The CRTC ruled that BCE would have to divest the Citytv stations in order to get approval for the larger Chum deal.

Telus (TSX:T) and cable provider Cogeco (TSX:CGA) were scheduled to give testimony later Wednesday.

Quebecor Inc., telecom company Telus and cable provider Cogeco are also against the deal, saying Bell will own too much of the market.

Cogeco and Telus have already voiced concern about the deal, which they say would give Bell too much control over the country's broadcasting landscape.

Bell has said the acquisition of the Astral media assets will provide more competition in Quebec's French-language market, which is dominated by Quebecor. It says that with the acquisition of Astral, it will own 33.5 per cent of the English language TV viewing market and 24.4 per cent of the French-language market.

The deal aims to create a media powerhouse that's poised to take on rivals in providing digital content to consumers through online services and mobile devices like smartphones and tablet computers.

The ACTRA union, which represents performers across Canada, supported the deal -- with conditions.

Union president Ferne Downey said ACTRA is relying on the CRTC to make sure Bell doesn't own more than 35 per cent of the English market so that strong, competitive Canadian media companies can continue to emerge.

"If you do that, we are prepared to support this transaction," she said. "But not without hesitation."