Premiership clubs will not return to training for another two weeks at least, ending hopes of a resumption of the season in early July.
The Professional Game Board (PGB), a panel made up of the power-brokers of English rugby, have agreed "more time is needed" to plan a safe return.
Some directors of rugby have stated up to eight weeks' training is required before players are match-fit.
It means the season may not resume until August at the earliest.
Premiership Rugby had targeted the first weekend of a July as a 'best-case scenario' for matches to resume.
The PGB includes representatives from the Rugby Football Union, Premiership Rugby, the Rugby Players Association and Championship clubs.
"The group agreed that although a huge amount of work is being undertaken to enable a safe return to training for Premiership clubs, more time was needed to ensure that players, staff and officials can return to a safe training environment, and that is not expected to be in place for a minimum of two weeks," said Board chairman Chris Booy.
"Safety and welfare remains of paramount importance to all of us in the rugby community, and we look forward to the season resuming when it is safe to do so," he added.
If matches resume in late July or early August, the season will not end until September and could run on into October.
With international games still scheduled for late October and November, it would mean the 2020-21 Premiership season might not start until December.
However, relegated Saracens are meant to be playing in the Championship next season, with the new campaign expected to start in September as usual.
That throws up the bizarre prospect of Saracens being in the Premiership and Championship simultaneously, as well as in the quarter-finals of the yet-to-be-completed Champions Cup.