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.

The Iron nearly took the lead when Russell Penn headed Manny Parry's effort off the line.
It was one of the few highlights of the first half, and affairs did not spring to life until the hour mark.
Jack Midson broke the deadlock for Braintree with a firm header from Reece Hall-Johnson's cross.
James Bolton's close-range header was fielded by Sam Beasant as the Tynesiders pushed for an equaliser.
McLaughlin eventually provided it five minutes from time, and Gateshead could even have won it a minute later when Jordan Burrow fired wide when in on goal.
Report supplied by the Press Association.
Match ends, Gateshead 1, Braintree Town 1.
Second Half ends, Gateshead 1, Braintree Town 1.
Substitution, Braintree Town. Lee Barnard replaces Michael Cheek.
Gus Mafuta (Gateshead) is shown the yellow card for a bad foul.
Goal!  Gateshead 1, Braintree Town 1. Patrick McLaughlin (Gateshead) converts the penalty with a.
Substitution, Gateshead. Gus Mafuta replaces Danny Johnson.
Substitution, Gateshead. Luke Hannant replaces Sam Jones.
Substitution, Braintree Town. Ebou Adams replaces Chez Isaac.
Substitution, Gateshead. Wes York replaces Russell Penn.
Goal!  Gateshead 0, Braintree Town 1. Michael Cheek (Braintree Town).
Substitution, Braintree Town. Reece Hall-Johnson replaces Monty Patterson.
Second Half begins Gateshead 0, Braintree Town 0.
First Half ends, Gateshead 0, Braintree Town 0.
Danny Johnson (Gateshead) is shown the yellow card for a bad foul.
First Half begins.
Lineups are announced and players are warming up.
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.
[NEXT_CONCEPT]
Paddy McLaughlin's late penalty salvaged a point for Gateshead as they drew at home with Braintree in the National League.