Language society's BBC Carmarthen studio demo over S4C
Some 200 people have demonstrated outside the BBC studios in Carmarthen in protest at the plans for the Welsh language television channel S4C.
Cymdeithas yr Iaith Gymraeg, the Welsh Language Society, accused BBC Wales of "betrayal" by co-operating with the "London government" to take over S4C.
Among the speakers were former Plaid Cymru president Dafydd Iwan.
From 2013, S4C will be funded from part of the BBC licence fee. BBC Wales said the decision was the UK government's.
Last month, 20 people staged a sit-in at the lobby of BBC Wales' headquarters in Cardiff, blocking in the entrance.
Protesters want the corporation to change its mind about taking over the funding of S4C.
The channel faces a 25% budget cut by 2015 under funding changes by Chancellor George Osborne.
Cymdeithas said the changes will make the channel a "sub-department of the BBC" from 2015.
In a statement, it said: "We call on young parents who appreciate the Cyw and Stwnsh programmes for children, we call on rugby supporters that S4C has given such a financial boost to, we call on young people who want to see a future for their channel.
"This could all come to an end if we don't raise our voices now."
Following the protest at the BBC studios, demonstrators said they plan to travel to the Whitland offices of Conservative Carmarthen West and South Pembrokeshire MP Simon Hart.
Mr Hart had discussions with David Cameron around the time the changes to S4C's funding were announced.
S4C had considered seeking a judicial review over the UK government's decision to change the channel's funding arrangements but last month confirmed it had abandoned the plan.
A spokesperson for BBC Wales said: "The decision to change the funding arrangements for S4C was made by the UK government, not the BBC.
"Discussions are ongoing between the UK government, S4C and the BBC and further details will be provided in due course.
"However, Mark Thompson, director general of the BBC, Menna Richards, former director BBC Cymru Wales, and Elan Closs Stephens, BBC national trustee for Wales, gave evidence to the Welsh Affairs Committee in the House of Commons recently and Mark Thompson has also agreed to meet with Cymdeithas yr Iaith within the next few weeks."
S4C's budget is being cut as part of the UK government's Spending Review.
The BBC will take over part-funding of S4C from 2013, with the Department for Culture, Media and Sport reducing its grant by 94% over the next five years.
UK Culture Minister Ed Vaizey has said the UK government is "committed to Welsh programming and committed to S4C".