which one is correct form ??
Antidiscrimination legislation has only mitigated,rather than abolished, inequity in housing practices.


Antidiscrimination legislation has only mitigated,rather than abolishing, inequity in housing practices.

Both are OK, Sharad, but the paraller structure ('-ed' + '-ed') is preferred.
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silly qn..
mitigation was done in preference to abolishing.. abolishing was never done..

so we always say

"Antidiscrimination legislation has only mitigated in preference to abolishing, inequity in housing practices".

Correct ?? We can not say abolished in the above sentence as abolishing never happened. similiarly we can not say abolished when using rather than, because abolishing never happened..

Please let me know what i am getting wrong here..
Correct, but the reason is grammatical. 'In preference to' is prepostional and takes a noun (gerund) object. It has nothing to do with the occurrence of the abolition.

And check your commas-- there should be two or none.