The union representing journalists has called on the competition watchdog to block the proposed merger of Nine Entertainment and Fairfax Media into a single $4 billion media giant.

The Media, Entertainment and Arts Alliance says the “takeover” is the inevitable result of the federal government’s “ill-conceived changes to media ownership laws” and will reduce media diversity.

“With ongoing inquiries into the independence and long-term viability of quality journalism under way, the ACCC must block this takeover,” MEAA media president Marcus Strom said in a statement on Thursday.

The Australian Competition and Consumer Commission will scrutinise the proposed deal.

Nine chief executive Hugh Marks and Fairfax boss Greg Hywood are confident the merger will proceed.

An ACCC spokesperson said the regulator expects to commence a public review of the proposed merger once it’s received submissions from Nine and Fairfax.

Nine and Fairfax announced the $4 billion merger saying the new company – called Nine – will be 51.1 per cent owned by Nine’s shareholders and led by the network’s chief executive Hugh Marks.

One of Australia’s largest media operations, it will include Nine’s free-to-air television network, the website 9Now and Fairfax mastheads such as The Sydney Morning Herald and The Age.

Other Fairfax interests, including real estate arm Domain, streaming service Stan and Macquarie Media’s radio network, are also part of the deal. Among other assets, Macquarie Media owns radio station 2GB in Sydney and 3AW in Melbourne.

The Fairfax family has been synonymous with Australian newspapers and other media since John Fairfax bought The Sydney Morning Herald in 1841.

Dr Vincent O’Donnell, an honorary research associate and media commentator with RMIT, told the ABC the proposal was one of the “more likely mergers” since the government changed rules that previously restricted mergers between newspaper, television and radio interests.

“It will be one of the first steps to consolidate companies reaching all three media but also getting bigger,” he said.

“Australian media companies are minnows by comparison with overseas companies and, therefore, the capital demands they believe they need for future and development and improvement in media are harder to achieve simply because of their relatively small size.”

“All media companies in Australia are principally run by old white men in suits and that implies, of course, a certain conservatism.”

However, Mr O’Donnell said there was a risk of news and current affairs in Australia becoming even more concentrated.

“If Fairfax and Nine further consolidate their newsrooms then the number of eyes reporting Australia to Australians is going to be further diminished,” he says.

“That, in terms of what I would call the political information economy, is a bad thing.”

Nine chief executive Hugh Marks will take the top job at the new expanded company. Photo: AAP

In an email to staff on Thursday, Mr Marks described the deal as a “momentous moment for Nine’s future”.

Fairfax chief executive Greg Hywood said the company had gone from “being at the mercy of the non-stop global media revolution to being the best of its breed” in the past eight years.

“That is why Nine wants to merge their business with ours,” he told Fairfax staff in an email.

“Working through the detail will take a number of months but you can be assured that there will be plenty of Fairfax Media DNA in the merged company and the board.”

In a statement announcing the proposed merger to the Australian Stock Exchange early on Thursday morning, the companies said the new entity was expected to deliver $50 million in savings in two years.

Fairfax’s directors will recommend that Fairfax shareholders vote in favour of the merger. Three of the company’s directors will be invited to join the board of the new business, which will be led by Nine chairman Peter Costello.