Singh was earlier minister of state in the same ministry. Mishra resigned as the minister last week.
Giving an emotional farewell speech, Singh described Mishra as a father figure who has guided him as well as the ministry.
"I will always seek his support. He is like a guardian and will always remain so. I will always follow his teachings," Singh said.
Mishra (76) said that he resigned in deference to the wishes of the party leadership that people above 75 years should not remain in the council of ministers.
Meanwhile, quoting Singh the ministry said in a statement that he will strive forward to increase employment under MSMEs and ensure that the sector do not face any hurdle.
Mishra hopes that his successor will finish the pending works and fulfill the dream of the prime minister.