Thérèse Coffey said she “nearly died” due to the stress of being a government minister.
Speaking to BBC Radio Suffolk, the former environment secretary said she was admitted to hospital after “working [herself] into the ground”.
Coffey, 51, who had been widely tipped to be in line to be sacked by Rishi Sunak during his cabinet reshuffle, resigned from her role on Monday.
“Nearly five years ago I got so ill, I nearly, dare I say it, died,” she said. “I was in hospital for a month with some of the stresses that happen with ministerial life.
“A few years ago I certainly worked myself into the ground somewhat, but I learned a lot from that incident and that’s why I’ve always had a joy about life.”
Coffey, who was made deputy prime minister under Liz Truss, said in her resignation letter that she is returning to the backbenches because it is the “right time” for her to leave government.
In his response, Sunak thanked her for her “years of dedicated ministerial service” and her friendship to him personally. She was replaced as environment secretary by Steve Barclay, 51.
Coffey’s previous cabinet roles also included two months as health secretary under Truss. She was previously a junior minister at the Department for Environment, Food and Rural Affairs.
Ruth Leach, from Save the Deben – a group trying to clean up the Suffolk river – said she was “delighted” by Coffey’s departure from government. Coffey was also accused of being “complacent” in dealing with water companies, risking water shortages as well as extreme environmental consequences, according to a House of Lords committee.
Meanwhile, Rachel Smith-Lyte, East Suffolk council’s cabinet member for the environment, a member of the Green party, added: “I’m amazed she’s been around as long as she has, both in terms of being environment minister, which is laughable, and as an MP for this area.”