Mitchell made the pledge on gender parity just weeks after joining the project this summer.
The current workforce consists of 29% women.
But Mitchell fears that percentage could fall as the project moves from the office stage to construction on site.
In an article in the Guardian he wrote: “Just six years into the project, 29% of our 450-strong workforce is female.
“But we are at present a largely office-based team and I am acutely aware that we have yet to face the real challenge.
“We are likely to see a significant drop in the percentage of woman versus men when we are joined by the contractors to do the main works construction.”
Mitchell is determined to raise the profile of women in an industry where they account for just 10% of the workforce.
He said: “In responding to the fears about how we are going to achieve the unachievable, I’m happy to tell everyone who is interested that we are working to create a culture that finds out from women themselves what they want and how they think we can attract their counterparts.
“It’s not a bunch of blokes sat around a table making assumptions on why we think women don’t want to work in construction.
“We are finding out the true obstacles so that we can we try to overcome them.”
Figures for the project during the first six-months of this year show only 21% of 869 applicants for jobs with Thames Tideway were female.
Mitchell said: “At the peak of construction, we’ll be creating more than 4,000 direct jobs and another 5,000 indirect, and we need to make sure when we advertise those roles, we’re getting a far better rate of female applicants than we are now.”
Thames Tideway bosses are working with Westminster and Loughborough universities to discover the perceived obstacles for women in engineering.
Mitchell said: “Gender parity is a bold statement, and maybe it is too ambitious, but I don’t see the point in striving for anything less.
“If we achieve this goal, I believe it will change the face of construction for future generations.”