The BBC is considering making BBC Radio 5 Live online-only in radical cost-cutting measures as it seeks to fill a funding black hole.

The news and sport channel is the latest service to have come under review as the corporation tries to find savings to cover the £700m annual cost of free licence fees for the over-75s by 2020.

Insiders suggest that the station could even be axed, saving the BBC its £66.1m budget. However, given its reach outside affluent, urban listeners and in the north, such a move could prove unpopular.

The spotlight has turned on Radio 5 Live because of the high cost of sports rights and more people looking online for coverage of fixtures and news.

The latest BBC annual report said 5 Live’s audience fell below 6 million listeners last year and time spent with the station also “dropped to its lowest level, with listeners tuning in for just over six hours a week”.

The report said 5 Live has already been looking at “developing its own online presence, offering a growing range of short-form clips” so it may be well placed to move online-only, in the same way that youth channel BBC3 did last week.

Radio 5 Live has a content budget of £45.3m, down from £49.1m last year, but also spends around £17m on distribution and “general support”.

While that is a drop in the ocean compared with the additional costs the BBC is facing over the next few years, every little will help as the corporation faces an uncertain future in the wake of last year’s licence fee settlement. Any scaling back of 5 Live will be welcomed by commercial rivals such as TalkSport.

As revealed by the Guardian, the BBC has already been looking at the idea of shutting its 24-hour news channel. In November it emerged that it was having a rethink over the channel, which costs in excess of £110m a year to run, after assessing that the savings may only amount to £15m or £16m annually.

Closing Radio 5 Live, which was set up in 1994 as a national service to air breaking news, phone-ins and commentary of sporting events, would be controversial in some quarters.

However, crunch time is coming for the BBC as it tries to balance its books with the prospect of substantial cuts looming large.

In a pre-internet era Radio 5 Live firmly established itself as essential listening, especially for rolling news stories.

But since then 5 Live has gone through changes. Part of the station was moved up to the BBC’s new northern headquarters in Salford and in 2014 it had a huge shake-up with well-known presenters Victoria Derbyshire, Shelagh Fogarty and Richard Bacon departing.

A BBC spokesman denied there were plans to make Radio 5 Live online-only, saying: “There is no plan along those lines.”