While the 43-year-old admitted Alexa Chung, who is the current face of an M&S range, was "edgy and cool", Stankard said people would prefer a model who appeals to the average British woman - citing her thousands of readers as proof.
"Good morning this is an open letter to Robert Weston and Steve Rowe who are chief executive and head of marketing for Marks and Spencer," she began her post.
"Now guys, I hope you don't mind me being informal? I have a rather exciting opportunity for you. I have developed a tasteful and exciting blog which is really doing very well. An opportunity has come up for an exciting and forward thinking company to advertise with this excellent blog and I would like to give you first dibs on it.
"My blog has 40,000 likes but of the demographic that you really need to attract - women aged 35 to 44. I have regular posts that 100,000 people read and get this - I had a post that 3.7 million people read. That many people can't be wrong."
"There are a number of ways in which I can help you get back the ladies that you aspire to dress," she continued.
"I am a stylish mother of three delightful children. I do shop regularly with your store in Manchester city centre and the Trafford centre branch.
"I notice that you have done a fab collaboration with Alexa Chung. She's very edgy and cool and let's face it, everybody would like to be her but let's be honest we are all a bit sick with envy at her.
"I mean she's got near perfect legs and is so beautiful that Alex Turner has written a whole album about how he hasn't got over her yet."
"Anyway I digress as I am prone to do. What you need is me - not Alexa or Rosie. I can advertise your bastion of British style in a non-threatening size 12 warts and all kind of way," she wrote.
"There are a number of ways in which we could take this forward. Your people can talk to my people but you've only got a limited time before I have talks with Mr Lagerfeld. I am thinking affiliate advertising or you could just sponsor my page.
"I have testimonials from companies that I have helped and I'm fairly sure that I would pass a criminal background check.
"Let's not do a BHS guys."
The Huffington Post UK has reached out to Marks & Spencer for comment.