Baroness Grey-Thompson has resigned from the London 2017 Athletics World Championships board, saying her role had become "a bit tokenistic".
The 11-time Paralympic champion added: "I got to the point where I was going round in circles."
Her decision follows the departures of three other board members, including managing director Sally Bolton.
"There are some good people left, but they'll need a lot more support," said Grey-Thompson.
She added that her role was no longer "fun or interesting", adding she had "got tired" of being the one to raise Paralympic issues.
"It needs to be someone else because I don't feel I was having the impact in terms of taking that discussion on,' said Grey-Thompson.
A statement from London 2017 made no mention of Grey-Thompson's concerns, claiming she was resigning for other reasons.
It said she had taken the decision so she "dedicate her full attention to her work in the House of Lords" as well as her role leading an independent working group looking to safeguard people who play grassroots sport.
Heather Hancock and Martin Stewart also stood down last month, amid reports of differences with chairman Ed Warner, who is also head of UK Athletics.
London won the right to stage the championships by beating Doha in a vote in 2011 and will hold the event at the Olympic Stadium.