Rugby fans have accused the Welsh Rugby Union of undermining the four regions with its money-making stadium plans.
The WRU is in talks over hosting a Wales v Barbarians match in November and Bristol v Gloucester in December at the Principality Stadium.
However both games would clash with two key United Rugby Championship (URC) derbies between Cardiff and Scarlets.
Cardiff supporters have criticised the proposals as a "staggering" short-term fix that "devalues" the regional game.
In a letter to new WRU chair Richard Collier-Keywood, the CF10 Rugby Trust said it "could not fathom" why the WRU would look to host an international match on the same day as a regional derby.
Scarlets and Cardiff are due to meet in Llanelli on 4 November, the date that has been pencilled by the WRU to host Wales-Barbarians at the Principality Stadium.
The reverse fixture between the regional rivals at Cardiff Arms Park - 2 December - is the same day a Premiership match between Bristol and Gloucester is being explored.
"We knew 2023-4 was not going to be an easy season with the inevitable [financial] cuts. What we were not prepared for was the continuing undermining of the four professional clubs by the WRU," the letter reads.
"The optics of promoting a clash from a rival league at our national ground whilst simultaneously cutting the payments to our own professional teams to the bone is, quite frankly, staggering.
"It creates, or perhaps confirms, the impression that our governing body sees the professional game below Team Wales as expendable."
The financial crisis in Welsh rugby will see funding to Cardiff, Dragons, Ospreys and Scarlets cut by £2m - from £7.2m to £5.2m - next season, and reduced further to £4.5m for the 2024-25 campaign.
Cardiff saw its losses worsen, from £1.6m to £2.2m for the year ending 30 June, 2022.
'Do things differently'
WRU boss Nigel Walker says the game needs to explore extra revenue streams as they look to host more matches at Principality Stadium.
"We've got to think about doing things differently," he said.
"What we aren't going to do is be reckless, we aren't going to introduce things which will destroy the fabric of Welsh rugby but we do need to think of ways of raising revenues."
However the letter from supporters, signed by the trust's chair Lynn Glaister, highlighted that regions now only have 11 guaranteed home league and European games a season to generate revenue.
"The WRU expect the four Welsh teams to drive up their own matchday and sponsorship revenue. Yet the WRU seem to have already forgotten about this in the name of short-term thinking," she said.
"It seems there is no wider strategy for the Welsh pro game beyond finding new ways to squeeze every last drop of income from the Principality Stadium, regardless of the long-term costs to the game as a whole."
The kick-off to the 2023-24 URC season has been postponed to late October due to the World Cup in France.