Darcey Bussell, Craig Revel-Horwood and Bruno Tonioli are expected to remain on the panel but none of them is likely to take the place of Len, who stepped down last year.
The BBC has indicated the new head judge must have a traditional dance pedigree and not the more flamboyant Latin style.
A senior BBC source said: “We’re looking at a judge with a deep ballroom background, just like Len had. Strictly Ballroom, if you like.
This means it won’t be someone with Latin dance experience. This also rules out one of the three current judges, Bruno, Craig, or Darcey.
“We are planning to do screen tests over the next month, and will appoint before the summer.”
The battle for the £300,000 a year head judge job will be between current dancer Anton du Beke and Australian judge Jason Gilkison and bookies favourite Gary Edwards, from Essex.
Reports last week suggested Du Beke, who is a favourite with fans could be a front runner, and that he had even been screen tested for the role.
A source said: “He would be like a younger Len and the transition would definitely be a smooth one.”
Meanwhile Edwards, a judge on US show Dancing With The Stars, has been called a “ballroom giant”.
Some bookmakers are no longer taking bets on him landing the role.
Jason Gilkison worked as a choreographer on Strictly Come Dancing three years ago and was a judge on So You Think You Can Dance Australia.