The Welsh Rugby Union (WRU) has named nine clubs in its new Elite Domestic Competition (EDC) from 2024-25 and appealed for another to apply.
Aberavon, Bridgend Ravens, Carmarthen Quins, Ebbw Vale, Llandovery, Newport, Pontypool, Swansea and RGC 1404 will be in the competition that will replace the existing Welsh Premiership.
No Cardiff regional club is on that list and Merthyr will not bid.
Pontypridd and Cardiff still have the chance to apply.
In a statement the WRU said its board has "approved the re-opening of the application process to review the granting of the one remaining licence for the competition, appealing for eligible clubs to apply to allocate the remaining EDC licence".
Having initially announced the new structure in August 2023 the WRU expect the process to "be completed by early Spring".
As it stands, three of Welsh rugby's regions will be represented in the EDC from next season.
Ospreys will have Aberavon, Bridgend Ravens and Swansea in their area, while Neath say they have been denied a place by the WRU which they describe as "an appalling decision".
In a statement on the club website Neath say they were rejected because of a negative credit rating and financial position, a business plan that was "too ambitious" and a lack of a relationship with the Ospreys.
The club refutes the financial arguments and claim their lack of relationship with the Ospreys "is not from our end".
The statement concluded: "We reserve our judgement to advertise our next move and despite complying with all WRU deadlines they have offered other clubs the opportunity for entry.
"It's an appalling decision as I'm sure the public will agree."
Dragons will have Ebbw Vale, Pontypool and Newport in their region while RGC 1404 will be the north Wales representatives.
In the Cardiff region, Merthyr have outlined their position on social media.
The Ironmen congratulated the nine new EDC teams and stated: "We are excited to commence our new journey, one right for our long term sustainability. We also look forward to renewing old acquaintances.
"With more than 275 young boys and girls representing our age-group and girls community, coupled with a successful youth section, we are wholeheartedly committed to the development of young people. For rugby, for wellbeing and for their futures. Much more than a twenty-three."
WRU performance director Huw Bevan said: "We need 10 teams in this league if it is to perform at its optimum level.
"Our clubs must also meet the criteria for a licence, to ensure that we are producing the sustainable and successful elite competition we need in Wales.
"This is why we are going back out to our clubs to search for a tenth team ready to join this exciting new competition."