The chairman of the BBC Trust is expected to call for an "i-licence fee" to fund the BBC.

In a keynote speech at the Autumn conference of the Voice of the Listener & Viewer (VLV), Rona Fairhead will outline the public's desire for "evolution, not revolution" for tomorrow's BBC.

"While the licence fee remains, though, there is widespread support for modernising it to cover BBC i-Player and catch-up services," she is expected to say.

"This move towards an 'i-licence fee' for the digital age is, in our view, long overdue. The widely supported method of funding the BBC should be protected, but reformed for the 21st Century."

She will urge the Government to fulfil its promise as soon as possible.

"We welcome the Government's commitment to closing this loophole by extending the licence fee to cover public service catch-up television.

"It was part of what was agreed back in July, and we look forward to this being resolved by July 2016, as the Government committed."

BBC research, she will say, indicates the public's broad support for a universal form of public funding for the BBC - either through the licence fee or some form of household levy.

She will call on the Government to "rule out" funding via subscriptions.

"We would also like them to rule out a subscription or part-subscription model for funding the BBC's public services.

"There is little public support - less than a quarter of people - for a system that charges a basic fee for a basic BBC service and then more for top-ups or extras," she will say. "In our view, this won't build a better BBC; it would start to tear it apart."

The chairman is expected to state that the BBC "must not be treated like a government piggy bank to be raided when times are tough".

"If we want to build a better BBC, even in these still straitened days, there can be no more top-slicing," she will say.

As the debate over charter renewal intensifies into the new year, the chairman will also argue for the views of licence-fee payers to be taken into account.

"There is next-to-no public appetite for radical change in the BBC. The public want us to build an even better BBC, not to tear it down," she is expected to state in her speech.

"So, yes to intelligent, targeted improvements. No to total transformation. They want evolution, not revolution."

The chairman will suggest six new public purposes to give those who pay for the BBC a better idea of what it exists to achieve.

The first three deal with the BBC's historic mission: to inform, educate and entertain.

The last three public purposes would be: reflecting, representing and serving everyone in the UK; reflecting the UK to the world and contributing to the UK's creative economy.