Mr Milband had his "heart in the right place",
Ms Abbott recently said
Outspoken Labour MP Diane Abbott has been sacked as shadow public health minister by Ed Miliband.
She told the BBC: "I think Ed wanted more message discipline."
She recently questioned the party's stance on immigration and suggested that, although the Labour leader was "doing his best", he was being swayed by polls.
The news that Ms Abbott was being sacked came as Mr Miliband completed the reshuffle of his frontbench team.
In a blog on the Guardian website, Ms Abbott said the Labour leader had been "very nice" as he sacked her, and she had told him that his decision "must be right".
"My first thought was that I was sorry to be no longer working with Andy Burnham and the health team," she wrote.
"I am also sad to be leaving some of the good friends that I made in the public health world. My role enabled me to engage with some fascinating subjects, like the sexualisation of women and girls and I plan to continue working on those issues."
She concluded: "I have enjoyed being on the frontbench.
"But I plan to enjoy being a free agent on the backbenches even more."
The BBC News Channel's chief political correspondent Norman Smith raised speculation that her sacking could clear the way for Ms Abbott to stand as Labour candidate for London mayor in 2016.
Ms Abbott, a Cambridge graduate and MP for the east London seat of Hackney North and Stoke Newington, hit the headlines last year after saying on Twitter that "white people love playing divide and rule".
In 2012, Ms Abbott resigned from a cross-party group on counselling given to pregnant women by abortion providers, dismissing it as a "front" for those who want it outlawed.
For much of her career, Ms Abbott was known as something of a left-wing maverick, rebelling against the Blair-Brown governments numerous times on issues including a third runway for Heathrow, renewing the UK's Trident nuclear submarine system, tuition fees and the war in Iraq.
She also became a regular pundit on the BBC current affairs show This Week, sharing the sofa with former Conservative cabinet minister Michael Portillo.
She was promoted to Ed Miliband's front bench following her unsuccessful bid to become Labour leader in 2010, in which she came last out of the five candidates to stand.
In other changes to the Labour line-up confirmed on Tuesday, Shabana Mahmood has been moved from shadowing the department of business to shadowing the Treasury; ex-shadow housing minister Jack Dromey moves to the Home Office brief; Dan Jarvis moves from culture to justice; Luciana Berger moves from energy to health; Stella Creasy moves from Home Office to business; and Chris Bryant moves from immigration to work and pensions.