The BBC is preparing a complete revamp of its iPlayer streaming service in the face of competition from Netflix, as it prepares for a life beyond traditional television channels.

The move is the latest attempt by the corporation to deal with changes in the way that people consume television and maintain its relevance to younger audiences.

The BBC expects iPlayer to become the main way people view its programmes. Shows will be made available by default for up to a year, rather than the previous 30-day limit.

Although traditional television channels still account for the vast proportion of British TV viewing, and the broadcaster intends to focus on those channels and on-demand for the foreseeable future, the transition to streaming risks leaving the BBC behind.

The iPlayer service had a 40% share of the streaming market five years ago but this has collapsed to 15% after the explosive growth of Netflix – even before the launch of more rival services such as Disney Plus and Apple TV.

No date has been set for the relaunch, which will be the service’s fourth major revamp since it launched 12 years ago. It will retain its name but the “look and feel” will be changed, while all BBC channels and live events will be integrated alongside box sets.

In a speech on Monday, the BBC director general will describe the changes as “a new front door for British creativity”, as the broadcaster promises talent “unprecedented levels of creative freedom” and a “broader shop window” on BBC platforms. Tony Hall will also publicly accept that the corporation simply cannot compete in financial terms with the resources of its US rivals.

Hall previously said that “new entrants” into the streaming market, such as Disney Plus and Apple TV – which are both due to launch before March 2020 – will shake up the existing order. The revamp of the BBC’s streaming service is described as a direct response to the shifting landscape by the broadcaster.

Disney Plus will launch in the US in November with Star Wars, Pixar and Marvel franchises on the service, which costs $6.99 (£5.40) a month compared with $13.99 for Netflix. Apple TV will also be available in November for $4.99 per month, as Netflix is put “under siege” by the new ventures.

The iPlayer relaunch will be essential as the BBC attempts to compete in an increasingly crowded marketplace, as younger viewers are attracted by rivals such as Netflix. The move also risks angering ITV by undermining the joint BritBox venture, which is due to launch this autumn priced £5.99 a month and is being pitched as a cheaper additional streaming service for consumers who already subscribe to Netflix.

Charlotte Moore, the BBC’s director of content, said: “iPlayer will become the heart of everything we do; the gateway to all our programmes – a ‘total TV’ experience, which will bring everything you want from BBC television into one place for the first time.”

Despite iPlayer pioneering UK streaming when it launched in 2007, its market share has plummeted in the face of new arrivals, while being hamstrung by regulatory constraints – such as only being able to show programmes for 30 days after broadcast. In August, Ofcom, the broadcasting regulator, gave the BBC the go-ahead to increase the amount of time that content is available on iPlayer.

In a press release the BBC said it was finally removing “the burdens of excessive regulation” in order to “push further and faster than ever before”. But some independent producers have raised concerns.

John McVay, the chief executive of Pact, the body that represents the UK’s independent TV production industry, said in August: “The BBC has consistently sought to strong-arm suppliers into giving the BBC these rights for no compensation and without a proper agreement.

“Pact has warned its members three times since April that the BBC has not yet reached an agreement with Pact for its ambitious plans.”

Previous changes to established BBC streaming products have not gone smoothly. The broadcaster was criticised for “ignoring its audience” over the decision to turn off its iPlayer radio app and replace it with the BBC Sounds app in an attempt to attract younger listeners.

The decision was announced last November but as the switch-off began in September this year, users complained that BBC Sounds was only available on new operating systems including Apple’s iOS 11, Android 5 or Amazon OS 5 or newer, meaning those with older operating systems were unable to use it.

A spokesperson for the consumer group Voice of the Listener and Viewer urged the BBC to give more time for the transition. James Purnell, the BBC’s radio and education director, said in a blogpost that supporting older operating systems did not offer “good value for money for licence fee payers”.

He said: “If people’s devices aren’t capable of running a supported operating system, in most cases they will still be able to access BBC Sounds on that same device via a web browser (eg Safari, Chrome).”