A group of MPs is urging the Welsh Rugby Union to pledge to treat all four of its regions equally, amid splits over WRU plans for a two-tier funding system.
Scarlets and Ospreys did not join Cardiff and Dragons in signing the new Professional Rugby Agreement.
After meeting WRU chair Richard Collier-Keywood and chief executive Abi Tierney on Friday, nine Welsh MPs issued a statement saying it was "imperative" no club is "handed an advantage at the expense of others".
WRU bosses have served a two-year notice on the current deal underpinning the professional game, but say they will "work closely" with all four clubs on a way forward with an "open mind" to "constructive and realistic proposals".