Richards said he could best support the bid without sitting on the board.
Manchester United chief executive David Gill, who holds an advisory role to England's bid committee, said it was a personal decision by Richards, but called for a period of stability following the resignation of six members earlier this month.
"It is interesting timing but that is a personal decision," Gill told Reuters.
"It is key (that there are no more changes to the board) but I think you will find that there are committed people on it and we have to draw a line in the sand; that's the board, lets move on and get on with it," Gill added.
Richards released a statement earlier on Tuesday announcing his decision to step down.
"With the recent changes to the England 2018 bid team structure, I feel I can now best support a successful bid without the necessity of sitting on the board," Richards said.
"My positions as Premier League Chairman, FA Board Member and Chairman of The FA's International Committee provide me with ample opportunities to bang the drum for English football, and the bid particularly, right across the world, which I will continue to do wherever and whenever I can."
England organisers were criticised by FIFA vice-president Jack Warner last month who said their bid lacked "stardust" and was falling off the pace.
Prior to Richards announcement, Gill had told Reuters that a boardroom reshuffle has quelled those fears.
"A very big board is difficult to manage. The board now is much tighter and much more cohesive," Gill said.
COMMITMENT
In an interview with Reuters after Richards' resignation, Gill said:
"Obviously I was surprised to see it but on the other hand it was a personal decision."
"I think one shouldn't read more than that into it. The Premier League is fully committed to it, all 20 clubs are and that is evidenced by the discussions we had with the FA meeting last week," Gill added.
"I think you can see from his statement that he remains very committed to it (the bid) and I think he will genuinely use all his best efforts to support it."
In his statement Richards, who had been invited onto the board partly to improve relations with the Premier League, said he believed England has all the right attributes to host a successful FIFA World Cup.
"Our challenge now is to convince the 24 members of FIFA's ExCo of that. This must be our focus and priority going forward," Richards said.
England are vying for the 2018 World Cup along with Australia, Russia, Spain/Portugal, United States, Japan, Holland/Belgium, Mexico and Indonesia.
"We have to draw a line in the sand and move on, it is what it is but ultimately it is not a board that wins a bid it is individuals," Gill added.
The successful bids are set to be announced in December 2010.
