Former British home secretary Charles Clarke said prime minister Tony Blair had decided that keeping him at the Home Office would "stand in the way" of reform in the wake of the foreign prisoners scandal.
Speaking outside the Home Office, Mr Clarke, who was removed from office today, said: "The prime minister, as is his right and responsibility, has made the judgment that my continued occupation of the post of Home Secretary is likely to stand in the way of continued reform that remains necessary.
"Although I do not agree with that judgment, I entirely accept his right to make it."
Mr Clarke later said he turned down a number of cabinet positions offered to him after his dismissal.
Earlier, Mr Blair released a statement announcing his decision to remove Mr Clarke from his position. "I am very sorry Charles Clarke has decided to leave the Government and return to the backbenches.
"Charles has always been an excellent minister and highly valued colleague in a series of important posts, he said.
"He took on the very difficult job of Home Secretary with his customary energy and determination and can look with pride at the reforms he has driven within the Home Office. In particular, he was a tower of strength in aftermath of 7/7," Mr Blair said.
"However, I felt that it was very difficult, given the level of genuine public concern, for Charles to continue in this post. I was keen not to lose Charles' talents from Government and offered him a number of other Cabinet posts.
"But I understand his decision to leave the Government and know he will continue to be a major figure in our party," the statement said.