They have asked the Parole Board to postpone his freedom until the outcome of a potential judicial review of its decision to let him out.
Worboys, 60, is expected to walk free as early as the end of next week after being granted parole.
He has served a year more than the minimum eight-year sentence he was given for one rape, six sex attacks and the drugging of 12 women he duped into accepting a ride in his taxi.
The two women need to raise thousands of pounds for legal fees to mount their legal challenge.
Police believe Worboys attacked