The singers - who are part of the girl group with Una Healy, Rochelle Humes and Frankie Sandford - are often seen wearing glamorous couture on the red carpet, but they admit they tend to shop more in budget-friendly stores.
Vanessa said: ''I love the high street! Topshop, Reiss, Urban Outfitters... all of them. You can't go wrong.''
Mollie added: ''I like Reiss, French Connection, Mango and Oasis the most.''
Despite their love of high street clothing, Mollie, 26, isn't opposed to splashing out on designer brands, especially luxury handbags.
She said: ''I spent over £1,000 on a bag. I didn't tell my parents that! I just said, 'Oh, it's a high street one.' ''
The 'What About Us' hitmakers spend countless hours on their hair and make-up to ensure they look fabulous at all times, but Mollie admits she longs for days off so she doesn't have to worry about her appearance.
She explained: ''Even wearing foundation on our day off feels like work, so it's really nice when you have those days when you can just stick your hair up in a bun and go without make-up.''