Diane Abbott has warned she will enjoy being a "free agent" on the backbenches after being sacked by Ed Miliband.
The shadow public health minister became the latest casualty of the Labour leader's reshuffle as he looks to the next election.
Ms Abbott, who ran for the leadership against Mr Miliband, shrugged off the demotion - declaring "I'll live".
In a sign of things to come, she immediately challenged the party's policies on immigration, nuclear weapons and the economy.
Writing in The Guardian, she declared: "I have enjoyed being on the frontbench but I plan to enjoy being a free agent on the backbenches even more."
Her removal follows high profile sackings by the party leader on Monday, in what was dubbed a "cull of the Blairites" by critics.
Shadow work and pensions secretary Liam Byrne and shadow education secretary Stephen Twigg both lost their frontbench jobs.
Ms Abbott was the first black woman MP when she joined Parliament in 1987 and is considered a potential future candidate for Mayor of London.
A prominent figure on Labour's left wing, the politician is regarded as one of the most independent-minded MPs in the House of Commons.
She recently questioned the party's approach on immigration and suggested Mr Miliband was being swayed by opinion polls.
In the summer, she also caused controversy by declaring she would quit if the party backed military action in Syria in a Commons vote.
Labour ultimately decided to vote against the Government, inflicting a humiliating defeat on David Cameron, so Ms Abbott stayed put.
After being told she was out by Mr Miliband, the MP for Hackney North and Stoke Newington went public with her concerns about a string of issues.
She questioned Labour's acceptance of Government cuts, calling for a "more far-reaching critique of austerity" and suggested Trident should not be "untouchable".
And she repeated her call for a tougher stance on immigration, warning the party should not be "pandering to anti-immigrant sentiment".
Ms Abbott said she had "long despaired of the downward spiral of Labour's rhetoric" and argued it should have opposed the "immigrants' go home" vans far more quickly.
"Unfortunately the people around Miliband are terrified by the polling on immigration and have convinced him that we need to move right on the issue," she claimed.
On the coalition side, Norman Baker has scotched reports of a clash between him and his new boss Theresa May after he became Home Office minister.
The Home Secretary was said to be "spitting tacks" after Mr Baker was moved to her department to replace Jeremy Browne.
But the Lib Dem insisted they had had a "very friendly chat" following his appointment and would be able to work well together despite coming "from different places".
Mr Baker, who wrote a book linking the security services to a cover-up over the death of David Kelly, also insisted he "entirely respects" the work of British spies.
Senior Lib Dem Danny Alexander predicted Mr Baker would be an "excellent" Home Office minister and would allow the party to "sharpen our campaigning edge" in that area.
Meanwhile, Tory Robert Syms' estranged wife Fiona has attracted attention after reacting with fury to him losing his post in the Whips' Office.
She wrote on Twitter: "PM just fired father of my kids over the phone. Gave up chairmanship of a cttee to be a whip, worked hard and was widely acknowledged to be a good whip.
"He was utterly gracious and took it like a man, I am beyond furious. Loyalty counted for nothing."
She joked her children had "defected to Labour" and that in her husband's position she would be "fixing up drinks" with rebels, but said the Poole MP would remain "super loyal".
She later updated her Twitter profile to describe herself as an "ex-wife with big mouth" who was "prone to extraordinary outbursts", although this has now been removed.