S4C will be vulnerable to political interference if a Westminster government bill becomes law, the Archbishop of Wales has warned.
Dr Barry Morgan has written to Deputy Prime Minister Nick Clegg expressing concern at the Public Bodies Bill and asking Liberal Democrats to vote against clauses relating to S4C.
The bill increases ministers' powers to change the structure of public bodies.
The UK government said S4C was "not sustainable in its present form".
The bill has been through the House of Lords and is due to be debated in the Commons soon.
The archbishop wants a meeting with Mr Clegg, cross-bench peer Lord Elystan Morgan and former Welsh Language Board chairman John Elfed Jones.
The idea echoes a 1980 meeting between then Home Secretary Willie Whitelaw and the "three wise men": Labour peer Cledwyn Hughes, former Aberystwyth University Principal Sir Goronwy Daniel and a former Archbishop of Wales, Gwilym Williams.
That meeting was seen as decisive in persuading Margaret Thatcher's government to honour its promise to create the Welsh-language channel.
Dr Morgan writes: "S4C has proved to be a great social and cultural success and recent problems should not overshadow the fact that the people of Wales take pride in it.
"If the clauses dealing with S4C are not removed from the Public Bodies Bill, the channel will lose its independence and 40% of its funding and there will be no certainty about how the channel will be funded after 2015.
'Impossible to plan'
"It will, therefore, be impossible to plan for the future of Welsh language broadcasting, if indeed there will be a future.
"When S4C was first established, it was protected by legislation from political interference. With the passing of the Public Bodies Bill, it will have lost that protection."
But Baroness Jenny Randerson, a Welsh Liberal Democrat member of the House of Lords said his view is out of date.
"I think that the Archbishop's concerns were perfectly accurate some months ago, but it's been dealt with," she told BBC Radio Wales.
"My view is that now S4C is a great deal more secure than it has been for the last year or so and I believe that under the umbrella of the BBC... S4C has a very secure future."
From 2013, S4C will be funded from part of the BBC licence fee.
Earlier this month the Welsh Affairs Select Committee said that decision had been taken with "regrettable" haste.
The broadcaster is also facing a 25% cut in funding, and 2010 saw the departure of both chief executive Iona Jones and chairman John Walter Jones.
Former chief executive Huw Jones is the preferred candidate to be S4C's next chairman.
In March, former Plaid Cymru leader Lord Wigley tabled an amendment to the bill in the Lords watering down the clauses relating to S4C. The amendment was defeated by the government.
A spokeswoman for the Department for Culture, Media and Sport (DCMS) said: "The government is committed to the future of Welsh language programming and to the future of S4C as a strong and independent Welsh TV service.
"We fully recognise the iconic status of the channel and the contribution it makes to the cultural and economic life of Wales.
"The S4C model is not sustainable in its present form, which is why government concluded that the best way to secure S4C's future while delivering a better service is through a partnership with the BBC.
"DCMS, S4C and the BBC Trust are working on the governance structure which will ensure that S4C will remain as an independent service, retaining its brand identity and editorial distinctiveness."
S4C declined to comment.