Lancaster has been in talks with New Zealand's World Cup winning coach Wayne Smith about joining the England management team as backs coach through to the 2015 tournament.
Smith, who thrived in a similar management structure with the All Blacks, has already expressed his interest in the role and he is widely regarded as the best in the business.
But with Smith likely to be unavailable for England's summer tour to South Africa, Lancaster has turned his attention to finding a temporary third member of his senior management team.
And Catt, the London Irish backs coach, has been widely touted as the leading candidate for the temporary position alongside Lancaster and Graham Rowntree.
London Irish are not thought to have received an official approach from the Rugby Football Union for Catt, although that may not be necessary. He has a year remaining on his London Irish contract but he is reportedly leaving the club this summer as part of a cull of backroom staff.
England are playing their first ever three Test series in South Africa and with two midweek games also in the schedule, Lancaster is taking at least 40 players and therefore a number of "support coaches".
"There will be three main coaches but to do this tour with just three coaches would be a stretch so we'll need some support in there too," Lancaster said in an interview to launch the new RFU.com homepage.
"Short term we need to find a replacement for Andy for the tour and some support coaches who can come in and help out with the team that plays in midweek. And also on the sheer logistics of it - we're going to select 40-plus players and we want to make sure we give them the feedback they deserve.
"Long term as well I want to make sure we've got the best coaching team to take us not only through the QBE Internationals this autumn and next year's Six Nations but right the way through Rugby World Cup 2015."