United Nation Development Programme's India Urban Poverty Report, 2009 has pegged the number of slum dwellers in Uttar Pradesh at 44 lakh.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/ranks-third-44-lakh-slum-dwellers
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-lucknow
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uttar-pradesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/undp
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/poverty
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/india
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/slums
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/national-sample-survey-organisation-nsso
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/maharashtra
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/andhra-pradesh
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/jawaharlal-nehru-national-urban-renewal-mission-jnnurm
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/infrastructure-development