"I love to declutter. I don't think you need so much stuff in your life. It just weighs you down," says the singer and stage star, who will be enlisting the help of family and friends – including former bandmates Cheryl and Nicola Roberts – to Give Up Clothes For Good.
"You can make a difference by doing something so simple," she says of backing the initiative by high-street store TK Maxx that asks people to donate a bag of clothes in its stores to raise money for Cancer Research UK Kids & Teens.
If clothes no longer fit they don't last long in Kimberley's wardrobe, but some will never go for recycling. "My wedding dress, for sure," says Kimberley, who married Justin Scott in the Bahamas in 2016. They have two sons together, Bobby, three, and nine-month-old Cole, who she introduced to the world in an exclusive HELLO! photoshoot. "There are things of the boys too that I can't let go, the first clothes that they wore, like little hats and babygrows, I keep those for the memories."
She also has her costumes from her Girls Aloud days including the huge feathers that they wore on their farewell tour. "They are wrapped up and packed away in our garage as they are too big to fit in the loft," she laughs.
"I am definitely not back to my usual size at all yet, but I haven't really felt ready to do much exercise," says the busy mum. "I'm too tired, but I do need to do the gym. I just haven't got to that stage yet.
"I have started doing little seven-minute workout apps to try and get my head around the idea of starting to exercise again."
Kimberley's boys keep her on her toes. "Cole is crawling now. He is on the move and trying to stand up. He is in to absolutely everything. Bobby loves it too, he gets excited by all the milestones. He says to him, 'Come on, come to me!'
"When you have one baby you think it is hard, then when you have two you look back and think, 'Oh that was so easy.'" There are always two special 'aunties' on hand to help in the shape of Cheryl and Nicola. "They both adore the boys and I still see them as much as I can."
Could there be a baby number three on the cards for 2018, just like the Duchess of Cambridge? "Keep counting," laughs Kimberley. "I think more like 2019 or 20."
For more info, visit tkmaxx.com/uk/en/give-up-clothes-for-good.