England said she let her comrades talk her into going along with the abuse.
Wearing her dress green US Army uniform and speaking sombrely in a soft voice, the 22-year-old reservist told the judge that she initially resisted taking part in the abuse at the prison outside Baghdad, but ultimately caved in to peer pressure.
"I had a choice, but I chose to do what my friends wanted me to," she said, entering her plea on Monday, a day before the start of her trial.
The charges carry up to 11 years in prison, but prosecutors and the defence reached an agreement for a lighter sentence, the length of which was not disclosed.
"They were being very persistent, bugging me, so I said, 'OK, whatever'"
A military jury will convene on Tuesday to determine her punishment; she will get the lesser of the jury's sentence or the term agreed on in the plea bargain.
If she had been convicted as charged, she could have been jailed for 16 1/2 years.
The judge asked her about a photo depicting her smiling and pointing at a naked detainee's genitals while smoking a cigarette. England said she replied: "No, no way" at first when a fellow soldier asked her to pose for the picture.
"But they were being very persistent, bugging me, so I said, 'OK, whatever'," she told the judge.
Military image tarnished
The plea bargain settles one of the most prominent cases to come out of the Abu Ghraib scandal, which damaged the image of the US military and sparked outrage against the United States around the globe.
England became a central figure in the scandal after photos emerged last year showing her and others sexually humiliating Iraqi prisoners.
England (C) posed for pictures
with naked Abu Ghraib detainees
One of the photos showed her holding a hooded, naked prisoner on a leash. Another showed her smiling and giving a thumbs-up next to nude prisoners stacked in a pyramid.
England's lawyers have argued that she and others in her military police unit were acting on orders from military intelligence officers to "soften up" prisoners for interrogation.
But army investigators testified during hearings last summer that England said the reservists took the photos while "they were joking around, having some fun".
The judge, Colonel James Pohl, went through each photo while asking England about her actions at Abu Ghraib in the fall of 2003.
"I could have said no," she said. "I knew it was wrong."
"I could have said no. I knew it was wrong"
She told the judge that Private Charles Graner Junior, the reputed ringleader of the abuses and the man said to be the father of England's infant son, put the leash around the prisoner's neck in order to take him from one cell to another.
When the prisoner resisted, she told the judge, Graner said to her: "Hold this, I'm going to take a picture." Pohl asked if she thought the leash was a legitimate way to control the detainee.
"I assumed it was OK because he was an MP," England said of Graner. "He had a background as a corrections officer."
Graner was convicted in January on a range of abuse charges and sentenced to 10 years in prison.
England's lawyer Rick Hernandez said last week that the defence would present evidence during the sentencing that England had severe learning disabilities and mental problems. He said there had been no decision on whether she would testify.
Graner is expected to testify for the defence during England's sentencing as early as Tuesday.
The defence says England (L) has
England entered guilty pleas to two counts of conspiracy to maltreat prisoners, four counts of maltreating prisoners, and one count of committing an indecent act. Prosecutors agreed to drop another count of committing an indecent act and one count of dereliction of duty.
England, from Fort Ashby, West Virginia, is one of seven members of the Maryland-based 372nd Military Police Company charged with humiliating and assaulting prisoners at Abu Ghraib.
Four other members of the 372nd and two low-level military intelligence officers have entered guilty pleas, with sentences ranging from no prison time to 8 1/2 years.
The only soldier to stand trial so far is Graner. Specialist Sabrina Harman, a former Abu Ghraib guard, is scheduled to go to trial at Fort Hood next week.
Several investigations have been conducted, but so far only low-level soldiers have been charged, although the defendants have alleged that high-level officials condoned the abuse.