The Samoa and Gloucester centre, Eliota Fuimaono-Sapolu, could face disciplinary action after he said the schedule for second-tier sides at the Rugby World Cup was "like the holocaust, like apartheid".

Samoa have to win their final two matches, against Fiji and South Africa, to have a chance of progressing to the knockout stages and are angry at having to play Wales just four days after taking on Namibia.

"#IRB, Stop exploiting my people. Please, all we ask, is fairness. If they [Wales] get a week, give us a week. Simple. #equity #justice," wrote Fuimaono-Sapolu on Twitter.

"If is obvious the IRB is unjust. Wales get seven days, we get three. Unfair treatment, like the holocaust, like apartheid. F*** U.

"Give Wales 3 days off and give Samoa a week. We would kill them."

The IRB is investigating whether the outburst, which has since been deleted, contravenes the social media guidelines in the World Cup code of conduct. Fuimaono-Sapolu was warned about tweeting by Gloucester last May after he reacted to the Premiership semi-final defeat to Saracens.

"I would say the referee was a joke but I would be fined so I won't," he wrote then. "Saracens: horribly boring but very clinical. No wonder my Super 15 friends are making jokes about northern hemisphere rugby. Owen Farrell put more bombs on us than the US did on Osama Bin Laden. Genocide."

The tier-two nations find themselves in a vicious circle. The IRB uses money generated from World Cups to grow the game in developing countries, but 60% of that revenue comes from television who want the top teams to play only at weekends, leaving the midweek slots for the smaller nations.

It is understood the only way the IRB can solve the current fixture issue would be to reduce the tournament to 16 teams, which would undermine the very point of trying to grow the game. An IRB spokesman said: "There were many important factors that were taken into consideration in finalising the World Cup 2011 schedule.

"Central factors considered were fan appeal, spread of matches across New Zealand and broadcast considerations as well as player welfare. While it is unavoidable that some teams have a more compressed schedule than others, we have worked to ensure no team has two three-day periods in a row as well as minimising travel.

"The broadcast revenues that are generated by scheduling around the top nations' matches are reinvested by the IRB to increase the competitiveness of the likes of the Pacific islands, Russia, USA, Canada etc. We are investing more than £150million in the game at all levels between 2009-2012, including £45 million in additional strategic investments for Tier Two and Tier Three unions as a result of the commercial success of Rugby World Cup."