The Rugby Football Union would block proposals to expand the Guinness Premiership from 12 to 14 clubs.
Premier Rugby (PRL) confirmed over the weekend that talks have begun over the possibility of adding two clubs to the Premiership, a move which would be funded by the league's next television deal.
The thorny issue of ending promotion and relegation by ring-fencing the Premiership has also reportedly been up for discussion - but any changes would have to be approved by the RFU.
Twickenham have always considered promotion and relegation to be sacrosanct and reminded Premier Rugby that the concept remains enshrined in the eight-year deal, which runs until 2016.
And there is currently little interest at the RFU in backing an expanded Premiership.
"Making a change of this nature is not a decision for PRL and its broadcasters to make - it would require RFU approval and that is unlikely to be forthcoming at the current time," said a Twickenham spokesman.
"The concept of relegation and promotion is legally enshrined in the eight-year agreement between PRL, its clubs and the RFU which lasts through until 2016."
Veteran Wasps and England prop Phil Vickery does not want to see an end to promotion and relegation either - but he has backed a revamped Premiership.
Vickery hails from Cornwall and he would relish the chance for a team like Exeter to establish a Premiership presence in the south-west.
He believes an extended league campaign would also solve the problem of too many meaningless matches that clutter up the season - an implied criticism of the LV= Cup, which was controversially revamped this season.
"I would like to see a few more teams come up. Growing up in the south-west, an hour away from Exeter, if Jonny Wilkinson or Danny Cipriani was coming to play at Exeter you would be there like a shot," said Vickery.
"It is crying out for that kind of thing. I think it would be great. There is always trade off. Do you cap it? Do you stop the opportunity of a club living the dream and getting into the Premiership?
"I am in favour of getting Exeter up and Worcester back and getting more teams in the Premiership but I don't want to get rid of relegation."
Reports have stated that Premier Rugby would consider dropping the LV= Cup, the Anglo-Welsh competition which this season went into a confusing conference format.
Vickery said: "Without wanting to cause too much controversy, there are quite a lot of games throughout the season which don't actually mean anything.
"I am sure there is a way of incorporating some meaningful rugby into the season."