Here is the full text of the letters between Alan Johnson and Labour leader Ed Miliband.
As we have discussed, I have decided to resign from the Shadow Cabinet for personal reasons to do with my family.
I have found it difficult to cope with these issues in my private life whilst carrying out an important front bench role.
I am grateful to you for giving me the opportunity to serve as Shadow Chancellor of the Exchequer and for showing me nothing but support and kindness.
You are proving to be a formidable Leader of the Labour Party and will take the party from strength to strength in the years to come.
Thank you for your letter confirming your wish to resign from the Shadow Cabinet.
You have been an outstanding colleague and great friend for many years. In government you showed real leadership on issues that mattered to families across our country, promoting educational opportunity, introducing a constitution for the NHS and delivering neighbourhood policing.
"It has always been clear that you never lost sight of the reasons which first brought you into politics. As Shadow Chancellor you spoke clearly to the public, warning of the dangers posed by the gamble the Government is taking with growth and jobs. I particularly want to thank you for the support and advice you have shown me during that period.
I wish you all the best at this difficult time. I know you will continue to make a major contribution to public life and the Labour Party.