Here are the letters of resignation by junior government members and the prime minister's response:
TOM WATSON'S RESIGNATION
The Labour Party has been my life since I was 15 years old.
I have served the party at every conceivable level and your own leadership since 1994 in a dozen different capacities, latterly as MP for West Bromwich East, a government whip, and as parliamentary under-secretary of state at the Ministry of Defence.
My loyalty to you personally, as well as to the party and the values we stand for, has been absolute and unswerving.
The struggle to fashion the kind of credible, convincing, effective Labour Party you now lead has been the preoccupation of my adult years.
My pride in what our government has achieved under your leadership is beyond expression.
We have revolutionised the lives and expectations of millions of our citizens, combining social justice with prosperity in a way which is unprecedented in the history of our country.
Your leadership has been visionary and remarkable.
The party and the nation owes you an incalculable debt.
So it is with the greatest sadness that I have to say that I no longer believe that your remaining in office is in the interest of either the party or the country.
How and why this situation has arisen no longer matters.
I share the view of the overwhelming majority of the party and the country that the only way the party and the government can renew itself in office is urgently to renew its leadership.
For the sake of the legacy you have long said is the only one that matters - a renewed Labour party re-elected at the next general election - I urge you to reconsider your determination to remain in office.
As you know, I had a conversation with the chief whip last night, in which she asked me to withdraw my support from the 2001 intake's letter calling on you to stand down, or my position would be untenable as a government minister.
I have reflected on this overnight.
I cannot withdraw my name, and therefore I accept her judgement.
I do not believe that statements so far give us the clarity necessary to progress over the next year.
Nor do I believe that newspaper reports of potential dates which may have appeared since I signed the 2001 intake's letter can provide the clarity the party and the country so desperately need.
It is with the greatest regret, therefore, that I must leave the government.
Tom Watson MP
West Bromwich East
Thank you for your letter.
I am sorry it has come to this.
You did a good job as a minister and I thank you for it.
I know you have worked hard for the Labour Party throughout your life.
I also accept entirely that you are entitled to your view about the best way for the Labour Party to renew in office.
But as you will know from the long years of Opposition we have endured, Labour only came to power after putting behind it the divisive behaviour of the past and uniting around a modern vision for both country and party.
The way to renew and win again now is not to engage in a divisive - and since I have already made it clear I will be leaving before the election - totally unnecessary attempt to unseat the party leader, less than 15 months after our historic third term victory; but through setting out the policy agenda for the future combined with a stable and orderly transition that leaves ample time for the next leader to bed in.
We are three years from the next election.
We have a strong policy platform.
There is no fundamental ideological divide in the Labour Party for the first time in 100 years of history.
For the first time ever, we have the prospect not just of two but three successive full terms.
To put all this at risk in this way is simply not a sensible, mature or intelligent way of conducting ourselves if we want to remain a governing party.
So I am sorry we are in disagreement.
KHALID MAHMOOD'S RESIGNATION
It is with great regret that I am writing to you to offer my resignation from my position as parliamentary private secretary to Tony McNulty MP at the Home Office.
Our Labour government has achieved a huge amount for this country, investing in and reforming our public services and lifting millions of our most vulnerable citizens out of poverty. Your leadership since 1994 has been inspirational.
The party and the nation owe you a tremendous debt.
It is imperative that we continue this work for the good of our party and our country.
This has always been my primary concern.
It was what drew me into Labour politics as a very young man, and what has underpinned the unswerving loyalty I have always demonstrated to you personally and the party as a whole.
The party and the Labour government's work is more important than any individual.
Sadly, I feel that your remaining in office no longer serves the best interests of the party or the country.
Given which views, it is with the greatest regret that I must leave the government.
Khalid Mahmood MP
LETTER FROM FOUR PPS'
We have been honoured to serve as members under your leadership since entering
the Commons in 2001.
The process of renewal and reinvigoration that your premiership has inspired
is without precedent. In each of our constituencies remarkable achievements have
resulted directly from the policies of Labour governments since 1997.
All of us rightly regard ourselves as loyal to the Labour Party and yourself
over many years. We believe however that you have not ended the uncertainty over
when you intend to leave office, which is damaging the government and the party.
The letter signed by other parliamentary colleagues organised by Karen Buck fails to address this issue and we are unable to put our names to it.
We have vitally important Scottish Parliament, Welsh Assembly and English Local Authority elections next year and we must resolve this matter well in advance of
It is with great sadness that we feel under the circumstances we have no alternative but to resign as parliamentary private secretaries.
Wayne David MP, Caerphilly; Ian Lucas MP, Wrexham; Mark Tami MP, Alyn & Deeside; David Wright MP, Telford