Damian Hopley, CEO of the Rugby Players' Association, believes reducing the Six Nations by a week would put an unacceptable workload and pressure on international players.
Aviva Premiership clubs are understood to favour shortening the Six Nations to six weeks, with England and France starting later than the other four unions. However, this has not been formally put forward to the RFU's Professional Game Board and is highly unlikely to gain support if the clubs do press forward with the idea.
Hopley is adamant his members have not been consulted over the plan and he insists their voices must be heard when any changes are proposed. The next RFU PGB meeting is not until November and there isn't scheduled to be any item dealing with a shorter Six Nations.
Hopley said: "The players do not support shortening the Six Nations. Not one England player I have spoken to believes this is a good idea.
"Playing four autumn internationals in a row is not the same as the intensity of the Six Nations which is a different beast. It is the most popular global annual rugby competition and there is intense pressure on the players and [when] half the England squad have, unprompted, spoken up about the work load it shows how serious the issue is.
"The players have taken an incredibly mature view over all of the issues facing the sport and if we were a militant body we could have challenged all of the major concerns in the game but we accept that the sport in England would not exist without the support of the owners and the RFU. It has got to the point that the players' voice has to be heard in trying to find the right playing structure and when that is achieved the commercial success will follow.
"I have believed that for 19 years but every year there is a new plan put forward. What needs to happen is getting the players involved in meaningful dialogue to help make huge decisions to address all of the issues. In the absence of that we are going to continue to damage what we are all trying to achieve."