He said: "I fully understand the responsibilities and am aware I have no experience in coaching. But with the other people we have in place, we can get the job done.
"Since I've retired people have been asking me when I'm going to be coming back to sort it out.
"It's been good to get out of the game for a couple of years, but I'm really looking forward to getting involved again.
"A lot has been said by people I consulted about not wanting to ruin my reputation, but I'm not worried about that. I want people to think well of me but I'm not in this for ego."
Quizzed about the manner of Ashton's departure, Johnson said: "It's a little bit difficult. Brian made it clear he didn't want to be a No2 in the set-up. It might be a good idea to bring in some new blood and new ideas. Players do respond to good coaching.
"Of course I have sympathy for Brian, it's been very tough. I intend to speak to him this week."
Rob Andrew, the RFU's director of elite rugby who made the appointment, said: "I spoke to Brian this morning and he is very keen to continue working with the RFU. Hopefully we will sort that out. He asked me to say he will not be suing the RFU over this issue."