Hooker Henry Palmer, skipper Ben Roach, wing Fin Baker and centre Harri Ackerman were all on the scoresheet as the Black & Ambers ended their pool fixtures unbeaten. Harrison James kicked three conversions and a penalty.
Scrum-half Tudur Jones and prop Pedr Jones scored tries, while Billy McBryde kicked 16 points for RGC, who led four times during the match. Newport will face the Pool B runners-up in the Cup semis with the Pool B winners hosing the second-placed side in Pool A.
“It is fantastic to finish top of the group and secure a home semi-final; I’m really pleased for the staff and players, especially given the number of injuries we’re currently carrying,” said Newport head coach Ty Morris.
“The game itself was extremely tough. Credit to RGC, they’re a very good side who caused us problems throughout. Ultimately, our defence won us the game. Every player fought for each other right to the end, which was hugely pleasing to see.”
Pontypool (eight points), RGC (seven) and Carmarthen Quins (six) are locked in a three-way fight to finish runners-up in Pool A going into their final matches.
The sides finishing third and fourth in both pools with progress to the Plate semi-finals. Quins recorded their first win in this season’s competition as they beat Cardiff 15-7 courtesy of tries from wing Thomas Williams and scrum-half Rhodri-Lewis.
“On paper, they had a strong team – a high-quality backline and Corey Domachowski playing up front, so it was a good test,” said Quins director of rugby Steff Thomas.
“We were quite deep in our squad and to be fair, the boys stepped up and got a good result. Any win against Cardiff is a good win, but I was delighted to get the win with the squad that we had out.”
It was a third successive defeat in the pool for Cardiff, who cannot now make the Cup semis, but will still be looking to secure a positive result against Pontypool on Thursday night to progress into the Plate semis. RGC host Quins on Saturday.
In Pool B, No 8 Jacob Hopkins scored a last gasp try as Swansea snatched a 28-22 victory from the jaws of defeat at Aberavon. Moments earlier, Tyler Murvai’s try looked to have won it for the Wizards.
Hopkins scored in each half for Swansea, who also had hooker Jamie Cox and centre Jack Hoskins on the scoresheet. Josh Phillips kicked the conversions. Luke Davies and Scott Delnevo were the other Aberavon try scorers. Keillen Cullen kicked seven points.
Two tries for skipper Joe Franchi and one each for prop Adam Williams and replacement Dom Franchi set Ebbw Vale on their way to a 28-21 victory at Bridgend Ravens. Will Ford added the extras.
Harvey Nash, Lloyd Wilkins and Tommy Morgan replied for Bridgend. Wilkins (2) and Ben Burnell kicked the conversions.
Llandovery are top of Pool B on 18 points ahead of Ebbw on 12, with the two sides meeting at Eugene Cross Park on Saturday. Swansea and Bridgend have seven and five points respectively ahead of their clash on Friday night.
Aberavon, having lost all four games, are now out of contention for both the Cup and Plate semis.
Meanwhile it has also been announced that the previously postponed matches between Pontypool and Carmarthen Quins in Pool A and Swansea and Ebbw Vale in Pool B will not be rescheduled.
Both matches have instead been declared as 0-0 draws with the sides being awarded two points each.