The paper featured more photos of the two leaders inside above another headline: "Finest weapons at their command? Those pins!"
A columnist described Sturgeon's legs as "altogether more flirty, tantalisingly crossed ... a direct attempt at seduction".
Theresa May has said it was a "bit of fun", telling the Wolverhampton Express and Star: "You will notice that I am wearing trousers today!
"As a woman in politics throughout my whole career I have found that very often, what I wear - particularly my shoes - has been an issue that has been looked at rather closely by people.
"Obviously what we do as politicians is what makes a difference to people's lives. I think that most people concentrate on what we do as politicians.
"But if people want to have a bit of fun about how we dress, then so be it."
More than 300 people complained to press regulator Ipso about the front page.
In a statement, the Daily Mail said the piece was "a sidebar alongside a serious political story" and had been flagged as "light-hearted" and told its critics to "get a life".
A spokesperson for the paper said: "For goodness sake, get a life! Sarah Vine's piece, which was flagged as light-hearted, was a side-bar alongside a serious political story.
"Again for the record, we often comment on the appearance of male politicians including Cameron's waistline, Osborne's hair, Corbyn's clothes - and even Boris's legs.
"Is there a rule that says political coverage must be dull or has a po-faced BBC and left-wing commentariat, so obsessed by the Daily Mail, lost all sense of humour...and proportion?"
The coverage of the meeting generated a torrent of criticism on Twitter with members of the public branding it as "utterly puerile" and "sexist, derogatory trash journalism".
"Has anyone told the #DailyMail that we put the clocks forward by an hour, not back 3 decades?" one woman tweeted, referring to the country's switch to British Summer Time at the weekend.
Alan Rusbridger, the former editor-in-chief of the Guardian newspaper, highlighted the ridiculousness of judging leaders on their physical attributes by tweeting "Nice pins" above a famous picture of wartime leaders Winston Churchill, Franklin D. Roosevelt and Joseph Stalin at the Yalta conference in 1945.
The Daily Mail, which has a circulation of 1.45 million and reaches millions more online, backed Brexit in last year's referendum on Britain's EU membership.
Sturgeon, who heads Edinburgh's devolved government, wants Scotland to hold a referendum on independence before Britain leaves the European Union.
- AAP
