International Rugby Board chief executive Brett Gosper has vowed there will be a crackdown on clubs who fail to release players for 2015 World Cup duty.

It has been alleged by Fiji fly-half Nicky Little that Pacific island players are "blackmailed" by their European clubs not to represent their country or have pay docked while on national duty.

The primacy of international rugby is enshrined in the IRB's regulation nine but policing it is hard, with Gosper comparing the practice to tax dodging.

"The IRB will not accept that practice in not allowing players to play for their countries, for two reasons," Gosper said.

"It undermines the competitiveness of the game which we are investing vast sums of money in and every player should be able to live his dreams and not be compromised by pressure coming from his club as to whether he can play for his country.

"There are several sanction such as fines. We are going to police it very hard. We are looking at player contracts and a big array of areas where we are trying to tighten the bolts.

"It is like tax dodging. We can't perfectly ensure that there is no practice around the edges but we have to close as many loopholes to make it difficult and stigmatise the practice and make it unacceptable."

Ireland's Rugby World Cup 2015 games will take place at Wembley, Cardiff and the Olympic Stadium

The World Cup will be contested on a level playing field after organisers agreed they could "no longer tolerate" the unfair fixture schedules which undermined recent tournaments.

The commercial requirement for the major nations like England and New Zealand to play on weekends has previously led to the smaller nations having to play in midweek with little rest time.

"The message is that 2011 was the last time we could tolerate tier two nations having to face an unfair schedule," said John O'Neill, a director of Rugby World Cup Ltd.

The unfair practice has been largely rectified for the 2015 tournament, with New Zealand, Australia, South Africa, France, Scotland and Wales all pressed into midweek action.

Gosper said: "The rest days are equal for tier one teams as tier two teams.

Lawrence Dallaglio says there is a great geographical split in the RWC 2015 venues

"There is a very balanced rest day programme. That have been issues in the past where we have seen performances fall off at the back end of the pool stages for tier two teams because they don't have the depth and haven't had the rest days."

O'Neill insisted the 2015 fixture schedule should be the blueprint for all future tournaments, even in 2019 when the World Cup heads to Japan.

The Asian time zone will bring increased commercial pressures from the lucrative European television market, which will want the leading nations to play at weekends.

"The equity and fairness of this draw should be embedded in all future tournaments," O'Neill said.