Speaking to reporters here, Shettar said developmental works undertaken by BJP government were overshadowed by "confusion and other negative things" that helped Congress.
"More than the positive vote for Congress, negative vote for BJP has helped Congress gain majority,", he said, adding his party could not reach out to the people on its developmental works.
Shettar submitted his resignation as Chief Minister to Governor H R Bhardwaj who asked him to continue till alternative arrangements are made.
Asked who was responsible for BJP's electoral rout, Joshi said "all leaders are responsible."
To a question about the impact of B S Yeddyurappa, he said there were many factors which had caused the damage and "we will assess and rectify them."
Asked if Gujarat Chief Minister Narendra Modi failed to cast a spell for BJP in the election, Joshi said "when so much of negative votes were there, I will not attribute them to any central leader including Modi.