Denim was a strong fabric.
Rose Tyler sometimes wore denim jeans. (TV: Rose, The End of the World, Aliens of London/World War Three, Dalek, Fear Her, etc) She also sometimes wore denim jackets. (TV: Father's Day, Boom Town, Fear Her) She once wore a denim mini skirt, (TV: Boom Town) and also wore short denim overalls. (TV: Tooth and Claw)
Sarah Jane Smith tended to wear denim jeans. (TV: School Reunion, onwards; GAME: Lost in Time)
Martha Jones tended to wear denim jeans. (TV: Smith and Jones, The Shakespeare Code, Gridlock, Daleks in Manhattan/Evolution of the Daleks, The Lazarus Experiment, The Sound of Drums/Last of the Time Lords)
Donna Noble sometimes wore denim jeans. (TV: Planet of the Ood, Silence in the Library/Forest of the Dead, Turn Left, The Stolen Earth/Journey's End, The End of Time)
Amy Pond wore denim mini-skirts. (TV: Victory of the Daleks, The Vampires of Venice, Curse of the Black Spot; GAME: City of the Daleks, Blood of the Cybermen, TARDIS, Shadows of the Vashta Nerada) She also wore skinny denim jeans, (TV: The Impossible Astronaut, Dinosaurs on a Spaceship) and sometimes a denim jacket. (TV: Let's Kill Hitler)
Maria Jackson wore navy blue overalls when she moved to Bannerman Road. (TV: Invasion of the Bane) She wore denim jackets and denim jeans. (TV: Eye of the Gorgon, onward) She sometimes wore a denim mini-skirt. (TV: Warriors of Kudlak)
Jo Grant wore a steel blue denim pinafore when she first met Mark IV Daleks including a gold leader as well as their Controller and Ogrons during the Time Paradox Incident; (TV: Day of the Daleks) and when helping many versions of the Doctor and companions. (GAME: Lost in Time)
Melanie Bush wore a shirt and jeans of steel blue denim. (TV: Delta and the Bannermen)
Clara Oswald wore a sapphire blue denim shirt during her first meeting with Ashildr during a Mire invasion of 9th century Earth. (TV: The Girl Who Died)
Bliss wore a denim jacket. (AUDIO: State of Bliss)
Kathy Nightingale wore denim jeans. (TV: Blink)
Rani Chandra wore denim jackets. (TV: The Temptation of Sarah Jane, The Mad Woman in the Attic, etc.)
Clara Oswald wore a denim shirt when she and the Twelfth Doctor first met Ashildr. (TV: The Girl who Died)
Yasmin Khan wore denim jackets. (TV: The Witchfinders, Can You Hear Me?)
Tegan Jovanka wore denim jeans. (TV: The Power of the Doctor; WC: The Passenger)
Bill Potts wore blue denim jeans with black stripes on the sides. (TV: Knock Knock) She also wore a denim jacket. (TV: World Enough and Time)
Krasko wore midnight blue denim jeans. (TV: Rosa)
Rose Noble wore a denim jacket when she met the Fourteenth Doctor, Beep the Meep, and some Wrarth Warriors. (TV: The Star Beast)
Jack Harkness purchased denim jeans from a Topshop in Cardiff. Trine-E and Zu-Zana called it a "design classic", but considered it dated by the year 200,100. (TV: Bad Wolf)