Marler, who last year made himself unavailable for England's tour of Australia, said the shake up would force players to miss tournaments to retain their fitness levels.
"If we lost a rest week -- I think it's ridiculous," Marler told the Guardian newspaper.
"They can slap me on the wrist for that all they want but it's such a physical tournament, the game itself is getting more and more physical every week
"(And) if it makes the season longer they will have to manage boys better or the boys will have to start managing themselves more."
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RFU chief executive Ian Ritchie said the English players had not been consulted about the potential schedule changes as he shrugged off concerns over the removal of a rest week.
"We believe it is perfectly right to have a six-week competition as opposed to a seven-week one. We think it would improve it," Ritchie said.
"It would narrow the off-periods, help with the broader narrative. We think it is a good route."
As part of the reorganisation of the calendar, England's summer tours are set to move to July, while the English Premiership are planning to begin the 2019-20 season in September, as usual, but end in June.
(Reporting by Hardik Vyas in Bengaluru)
