Flight Crew Air Transport Pilot (ATP)
Workload
ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Issued New Clearance
Environment - Non Weather Related; Human Factors; Procedure
I am relatively new to this aircraft with about 350 hours in type.  Additionally; the First Officer (FO) had about 150 hours in type.  After flying the SEAVU2 Arrival with significant delay vectors and speed control; both fast and slow; from TNP all the way in to final approach; we were given 3 different runway assignments (25R; 24R; then 24L).  On third assignment; after being cleared visual approach to 24L; we were then told maintain 250 kts.  Due to significant wake turbulence from preceding aircraft; we told the controller we were unable to maintain 250 kts.  The situation at this point was that we were in night VMC; passing through about 4;000 feet; trying to reprogram the FMS; maintaining visual separation from aircraft we were to follow; aligning with the new runway and ensuring we did not impinge on the south side flow to 25R.  The controller expressed displeasure at our inability to maintain 250 kts.  Further coordination resulted in a speed of 230 kts but frequency congestion prevented better communication of the situation.  Additionally; the workload was too high to continue into the final approach fix at 250 kts.  While I sincerely appreciate the job the SOCAL controllers do in getting us in to LAX; I have a reasonable expectation to be in a position to make a stabilized approach.  That expectation would not have been met if we complied with the controller's request.  Either we are all working to achieve stabilized approaches or we will continue to have pilot/controller difficulties.
A319 Captain reported difficulty complying with ATC speed request because of workload which was heightened by multiple runway changes and wake turbulence from preceding aircraft.