GaneshS wrote:

I am looking for weekday pass which can be used for zone 1-3 only on
weekdays which is less than 26£. I have got a monthly pass, but dont
use it a penny during the weekends.


There isn't any such weekday-only ticket in London.

If you're only travelling on buses and the Underground then depending
upon the number of journeys you make and when you make them it's
possible that Oyster Pre-Pay (or Pay As You Go) could be cheaper.

A bus fare using Oyster Pre-Pay costs £1 between 0700 and 0930
weekdays or 80p otherwise; the fares for Tube journeys using Oyster
Pre-Pay are detailed he
http://tfl.gov.uk/tfl/fares-tickets/.../tubedlr.shtml

Oyster Pre-Pay isn't valid on most National Rail routes - the few
exceptions are listed on this TfL Oyster help answer:
http://tinyurl.com/78fu8.