Mahinder Nagpal, leader of the House in the north corporation, said the civic body had collected samples and sent them for testing after getting repeated complaints regarding inferior quality of water supply.
Only three of the 47 samples from south zone of the South Corporation were found unfit. However, Karol Bagh - which falls under North Corporation - threw up 10 unfit samples of a total of 75 tested by the civic staff. In the tests carried out with the DJB, five of the 20 samples were found unfit.
Narela in northwest Delhi had 20 unfit samples from a total 70 tested by the civic staff, while during the joint exercise, 20 of 56 samples were unfit.
"These tests have revealed shocking results. The Delhi government is responsible for the water supply and it should take necessary action," Nagpal said.
"DJB is alert to every issue of contamination," said Debashree Mukherjee, DJB CEO. She said "the results should not be taken as symptomatic for all of Delhi" as targeted sampling is done in areas where there are more complaints of contamination. "We isolate such clusters and then flush the lines again to zero in on the exact problem," she said.