LONDON --- Rugby Europe chairman Octavian Morariu believes continued development of tier two nations on the back of the Rugby World Cup is vital to the sport's global growth, but warned that tier three nations cannot be left behind.

The performances of Georgia, who qualified automatically for Japan 2019 by winning two pool matches for the first time in their history, and Romania in England sparked debate over whether lucrative tier one competitions such as the Six Nations should be opened up to further participation.

However, while hoping that may one day be the case, Morariu called for an intelligent and patient approach to growing the sport worldwide.

"This is one of the greatest legacies of this World Cup," Morariu told ESPN before addressing the Rugby Europe union members in Kensington on Monday. "The fact that everyone could see the progress of the tier two nations, this is something that we need to follow in the future. There is a lot of enthusiasm now, but I hope this enthusiasm does not fade away after the World Cup. We need to keep up the message -- the game must be more open and we must ensure more participation.

"This year between the World Cup and the Olympics is an interesting year to discuss how rugby can evolve and be developed in order to become a global sport.

"We must not fall into the trap where the second tier nations become closer to the first and leave a huge gap [to tier three nations]. This must be a very intelligent and organised process in which the second tier countries take the third tier with them, in the sense that we have a more equal and consistent number of teams that can play at a certain level.

"This has been the best World Cup ever and the figures are there to prove it. But we cannot sit and think 'We've done a marvellous job, fantastic, we can stop here'. We must go forward."

Georgia's showing plus their continued European Nations Cup domination raised questions over a potential inclusion into the Six Nations, with head coach Milton Haig pulling no punches in saying it would be the next level of development for his side.

But while Rugby Europe, which is responsible for the sport's promotion, development, organisation and administration on the continent, falls under the World Rugby umbrella, it does not govern the Six Nations with power ultimately lying with its respective rugby unions. Morariu admitted no formal discussions with the home nations had taken place but said changes to Europe's biggest tournament should be considered.

"The Six Nations should look carefully at opening the opportunity of opening the competition," he added. "Maybe promotion and relegation would not be the best model, but it is a discussion we need to have together and see how we can open the competition and enlarge it.

"The debate has now been launched by the media and the supporters. I hope the message has been heard and understood. It's not only about principles but developing the game and gaining markets by opening the game up to other European countries."

Octavian Morariu speaks to the media during the Rugby World Cup 2015 press conference© Tom Dulat/Getty Images for IRB

Morariu will suggest more teams be added to the Six Nations when World Rugby's congress meets in London this week. However, Rugby Europe Executive Committee member Archie Fergusson believes a more realistic approach would be to overhaul the Autumn Tests instead. "The Six Nations is also a very lucrative, commercial competition and it would be very difficult for other countries to break into that," he said.

"I can't answer from a personal perspective, but think for yourselves -- if you were part of that, would you wish to break it up? I don't think so. There is an issue there, whether it's commercial or political, but that's for others to think about.

"Perhaps there needs to be a higher intensity of competition there or trophies given for the Autumn Tests, instead of them being seen as warm-ups for the Six Nations. That is an area which could be developed in terms of intensity of the competition.

"You have a good mix there -- sometimes you have competitive tier two nations, sometimes you have southern hemisphere nations as well. What a great way it would be to develop tier two nations within World Rugby by having a mixture of southern hemisphere, tier two and Six Nations -- I think that is the route forward."