Ms Truss picked up 57% of the valid votes cast, compared with 43% for Rishi Sunak.
David Cameron managed an even bigger share in 2005, winning 68% of votes to David Davis’s 32%.
Ms Truss also fell short of the total secured by Iain Duncan Smith in 2001, who picked up 61% of votes versus Ken Clarke’s 39%.
In the two other leadership contests that have occurred under the current rules, in 2003 and 2016, the outcome was decided before a ballot of the membership could take place.
Liz Truss’s victory means this is the first Tory leadership contest since 2001 that the candidate with the most votes among MPs has not won the most votes among party members.
Rishi Sunak led his rival candidates in every round of voting among MPs and ended up with 137 votes in the final ballot, ahead of Ms Truss on 113 and Penny Mourdant, who was eliminated from the contest, on 105.
Boris Johnson and David Cameron both won the most votes among MPs and the party at large.
In 2001, Ken Clarke won the most votes among MPs but lost the ballot of members to Iain Duncan Smith.
Turnout for this year’s membership ballot was given as 83%.
This is down from a turnout of 87% in the 2019 ballot.