Wednesdays and Thursdays were rushed, taking 29 minutes, but Friday's preparations increased to 33 minutes as the weekend beckoned.
More than half of women said they would make an extra effort if they had a meeting or appointment with the boss.
Nearly a quarter said they would take more time over their appearance if there was a promotion up for grabs.
And one in 10 women received compliments on their appearance at the start of the week but said these tailed off as time went on. Four in 10 of those polled said every office has a woman who always looks impeccably turned out.
But opinion varied as to why this was, with almost half claiming those who look pristine have lots of money to spend on treatments.
A third said women who don't have the added pressure of being a mother look more groomed.
Another 48 per cent said women who looked glamorous and well turned out every day must be getting up at the crack of dawn.
The spokesman added: "There is an assumption that women who spend lots of money on clothes, skincare treatments and make-up are automatically going to be the most preened in the office, but that's not necessarily the case.
"Adopting a good skincare routine will pay dividends in the future.
"Although mornings can be rushed and cleansing, toning and moisturising can add on a couple of minutes it will pay off in the long-term.
"As far as the rest of your appearance is concerned, if you prepare your outfit the night before then you are halfway there."
- DAILY MAIL