Prime7 and the ABC, of course.

WIN's half-hour bulletin of ACT news, presented out of the network's Wollongong studios by veteran anchorman Geoff Phillips, had the biggest audience in the 6pm timeslot in Canberra last week, with a weeknight average of 17,002 viewers.

But the first half-hour of Prime7's relay of Seven News from Sydney won on Tuesday, Wednesday and Thursday nights and averaged 16,565 viewers for the week - falling just 437 viewers short of beating WIN News.

The WIN program won the first 30 minutes of prime-time on Monday and Friday nights when it attracted twice as many viewers as the new Canberra version of Nine News.

Presented from Sydney by former ABC News Breakfast weather presenter Vanessa O'Hanlon, Nine's new-look bulletin of local, national and international news ran a distant third between 6pm and 6.30pm, averaging 10,862 viewers.

Billionaire Bruce Gordon's privately-owned WIN has not faced direct commercial competition for local news viewers in the ACT since June 2001, when Prime axed its nightly bulletins in Canberra, Wollongong and Newcastle.

Nine, which last year dropped WIN as its regional affiliate after almost 30 years, is launching 15 versions of Nine News against WIN News in the southern and central NSW, Victoria and Queensland markets of its new broadcast partner, Southern Cross Austereo.

WIN's newly appointed network news director Stella Lauri said the debut ratings for Nine News in Canberra showed that "viewers recognise our experience and appreciate the dedication shown".

"Our Canberra team is doing what it has done better than anyone else over the past 27 years, which is provide Canberra and the surrounding regions with a dedicated half hour of news, sport and weather that's relevant to the viewers of the region," she said in media release issued on Saturday.

But WIN's relief at fending off Nine's challenge last week will be tempered by indications that Prime7 - with its less expensive relay of Seven News - is already benefiting from Nine's attack on WIN News.

While WIN increased its share of the commercial audience in the 6pm slot last week to 32.9 per cent (up from 30.7 per cent over the previous two weeks) and Nine's went backwards, Prime7's share grew from 22.9 per cent to 32.1 per cent.

Prime7 also won the hour between 6pm and 7pm, with Seven News averaging 16,692 viewers, WIN News and the first half of The Project averaging 15,273 and Nine's hour bulletin drawing 12,682.

The weakest night for WIN News was Wednesday, when it slipped back to third place as Canberra viewers evidently turned to Seven's Mark Riley and Nine's Laurie Oakes for coverage of Prime Minister Malcolm Turnbull's stinging Question Time attack on Bill Shorten.

Meanwhile, the ABC's 7pm Canberra bulletin - with new anchor Dan Bourchier - continued to dominate its timeslot with a nightly viewership (38,746 viewers) that dwarfed the audiences of its commercial news rivals.

The rollout of localised Nine News bulletins continues on Monday in Wollongong, followed by Orange, Dubbo and the Central West on February 20 and Wagga Wagga and the Riverina the week after.

With small teams of reporters based in each market, the Nine bulletin and its local stories are compiled and presented by O'Hanlon from Nine's Sydney studios in Willoughby.

Southern Cross Austereo has carried Nine's shows and branding since last July after striking a $500million, five-year program supply deal that forced WIN to partner with Network Ten.

Bermuda-based Mr Gordon, as well as owning WIN, is the largest shareholder in both Nine and Ten, but is prevented from taking his holding above 15 per cent due to media ownership rules.

WIN has repeatedly warned that the 3000 hours of local content it broadcasts each year is "not a profitable exercise" and increasingly at risk without media reform.