Following a second meeting in 24 hours, the executive of the powerful 1922 Committee decided against cutting the amount of time needed between confidence votes in a Tory leader, from one year to six months.
In the face of growing anger about the failure to deliver Brexit on schedule, Mrs May promised her MPs to quit as soon as the Withdrawal Agreement is approved by parliament, but the UK's exit from the EU has now been delayed until October.
With opinion evening divided, senior MPs on the 1922 held two ballots behind closed doors on Wednesday afternoon, and decided against a change to the party constitution.
But the Committee is to ask Mrs May for "clarity" on how long she plans to remain PM if her EU Withdrawal Agreement fails.
Following the meeting, 1922 Committee chairman Sir Graham Brady said: "The decision was first of all that we determined there should not be a rule change to remove the 12-month period of grace during which a second confidence vote cannot be held.
"We further determined that we should remind colleagues that it is always available to them to write to me as chairman of the 1922 Committee raising concerns or setting out their thoughts, including concerns about the leadership of the party, and that the strength of opinion would be communicated by me to the leader of the party should they decide to do so.
He added: "I think the 1922 executive is asking on behalf of the Conservative Party in Parliament that we should have a clear roadmap forward."