The Chelsea manager was highly critical of the young England winger after his comeback from injury in Wednesday’s 7-1 Carabao Cup win over Grimsby.
And last night Lampard doubled down on his position on the 18-year-old, who signed a new £120,000-a-week contract a few weeks ago but who saw a transfer request rejected in January when Bayern Munich made several bids for him.
The Chelsea manager said: “I say it as I see it. I know Callum’s talent – he has got huge talent.
“Hence why the club were so keen to get him signed up and we’re all delighted with that.
“But there’s a lot of work for Callum to do.
“Raheem Sterling is an incredible example of a player with great talent whose work ethic added to that talent and improvement through absolute dedication has made him the complete player we are all wowed by.
“He is exactly the model for Callum, because he has those talents. I want Callum to be the absolute best, because he has the potential.
“A lot of that is handing out some hard truths – and I saw hard truths in the game the other day – ways he can improve. He needs to listen to them and he will. And then he can be that player for us.
“Some young players need cajoling, some definitely need tough words to help them improve.”
Lampard, whose side meet Brighton at Stamford Bridge this weekend still looking for their first home win in the league, admits he has been delighted with the way the fans have reacted to his young team’s football.
But the Chelsea manager now knows he owes the fans a home win.
He said: “I bump into the fans all the time. I live five minutes away from the ground, it’s hard not to.
“People are very supportive about what we’re trying to do – cabbies, people when I walk the dog. It’s nice to see that.
“But I don’t want too much sympathy when I don’t win.
“I want to repay that – and quickly. The fans see that it may take time, which is pleasing. But I don’t expect credit because I played for the club or because of what we won in an era gone by.”
Chelsea lost 2-1 at home against Liverpool last Sunday, but put up a rousing performance, and Lampard said: “Fans will always react to passion, desire, work ethic and fight. Sometimes the result is not the biggest thing – sometimes.
“But they will always enjoy winning first and foremost.
“I want to win games. The young players have brought a different dimension – the fans are loving seeing them come through. But now I want to give them wins.”
Probable team (4-3-2-1): Arrizabalaga; Azpilicueta, Christensen, Tomori, Alonso; Kante, Jorginho, Kovacic; Willian, Mount; Abraham.