SBS onsold broadcast rights for most World Cup games to Optus Sport, with Fairfax Media reporting that deal was worth approximately $8 million.

It threatens to cost the telco much more in reputation damage, with technical issues - causing poor-quality match footage or no vision at all - having plagued its broadcast of the tournament's opening weekend.

Many football fans, including those who signed up for a $15 package specifically to watch World Cup games, are furious because they've been unable to access the Optus broadcast.

Optus chief executive Allen Lew apologised "unreservedly to all Australians" on Sunday, but there were further issues that night.

SBS confirmed on Monday night it will air all World Cup games for the next 48 hours following talks with Optus, with Lew saying sorry once again.

"There's no doubt this had adversely affected the Optus brand ... everybody is very disappointed, to put it mildly," Lew told reporters on Monday night.

The situation, which is being monitored with interest by many sporting bodies in Australia given streaming is widely considered the future of broadcasting live sport, has already attracted the interest of the Australian Competition and Consumer Commission (ACCC).

"We are seeking further information from Optus on what steps it is taking to comply with the Australian Consumer Law," an ACCC spokesperson said.

"Under the Australian Consumer Law, services must be fit for the purpose and deliver on what was promised.

"Consumers impacted by the streaming problems are advised to contact the service provider directly."

Optus offered disgruntled customers a free 'Fetch' set-top box on Monday. However, this created more angst as some users reported difficulties collecting these units from local stores.

Optus insists its stores will be restocked regularly this week.

Industry sources told AAP it's likely the provider spectacularly underestimated demand for the service.

"We obviously did not (anticipate demand)," Lew said.

"We will take full responsibility."

Demand is likely to grow as the tournament unfolds; Optus has exclusive rights to broadcast some quarter-finals and round-of-16 games.

Aside from issues during live matches, some users have complained about difficulties in accessing highlight packages and replays on demand.

"Optus states the number of people affected are less than five per cent of their viewerships," SBS chief executive Michael Ebeid said, having consulted the telco.

The World Cup is on the nation's anti-siphoning list, but only the final and matches involving Australia.

Ebeid cited 2014 budget cuts as part of the reason his network, Australia's World Cup broadcaster for the past 32 years, signed the Optus deal.

"It enabled us to retain the World Cup, where we may not have been able to afford to do it on our own," Ebeid told radio station SEN.

"SBS is very limited in things like its advertising revenue."

Australian Associated Press