Daniel Pelka was murdered in Coventry in March 2012 by his mother and her partner.
City council leader Ann Lucas said more children's social workers was "the answer" to the "huge pressures" her staff faced.
The council said cases rose from 3,085 in March 2013 to 4,529 in March 2014.
Ms Lucas said reports of suspected child abuse had increased dramatically since Daniel's death.
The council currently has a team of 197 children's social workers.
But, Ms Lucas said the authority had grown increasingly reliant on agency workers, who were more expensive and did not provide the same consistency on cases.
"We have no choice - we have to take in agency workers," she said. "There aren't enough trained social workers.
"Social workers also have a huge burn-out rate. These people are working at the coal-face.
"I take my hat off to them. I think they are heroes - I don't know why they do it. They are castigated at every turn."
One social worker Chris Horne, told the BBC: "The bottom line is if there's more work than there are social workers, we're always going to struggle."
Senior social worker Sarb Bhambra added: "Staffing is always an issue. It's impossible to manage all the priorities because everything is a priority and there's only so many of us."
A freedom of information request reveals the number of reports of suspected abuse in Coventry has soared by 40% since 2011. There were more than 21,000 in 2013.
The results of an Ofsted inspection of children's services in Coventry are expected to be released in the coming weeks.
Children's social workers on a council that "missed chances" to save a four-year-old boy's life say they need more staff to cope with rising caseloads.