Ilford North MP Wes Streeting is to take a step back from politics while he undergoes treatment for kidney cancer.
Mr Streeting, 38, said the diagnosis had come as “an enormous shock” but the prognosis was good as the disease had been caught early.
In a video message posted on his Twitter feed, he said he would not be returning to work until he had made a full recovery.
The announcement comes less than a week after he was promoted to the shadow cabinet by Labour leader Sir Keir Starmer as shadow secretary of state for child poverty.
In his message, Mr Streeting said: “Back in early March, I went into hospital with a kidney stone and, at the time, a scan identified a lump on the same kidney.
“Around a month later, in April, unfortunately that lump was diagnosed as kidney cancer.
“While receiving a cancer diagnosis at the age of 38 has come as an enormous shock, the good news is because of that kidney stone the cancer has been caught early, my prognosis is very good, and I should make a full recovery.
“But it does mean I have to take time off work for treatment.
“My family have made it very clear – and actually so has Keir – that I will not be coming back until I’ve made a full recovery.
“Hopefully that won’t be too long but in the meantime, bear with me and thank you very much in advance for your support.”
Sir Keir said the thoughts of the entire Labour Party were with Mr Streeting and his family.
“Wes is a friend and a colleague and I know he will come back from this even stronger and more determined than ever before,” the Labour leader said.
“I cannot wait to see him back in Parliament as soon as possible.”
Mr Streeting, a former president of the National Union of Students, is regarded as one of Labour’s rising stars.
In his statement, he paid tribute to family, friends and colleagues who have supported him through a “really difficult period”.
“I also want to say thank you to all of the Labour candidates and activists I joined on the doorstep because, without knowing it, they made such a difference to me during what was a really difficult time, taking my mind off things and helping me to crack on as normal.
“I will be taking time off from the end of next week and, during that time, if you're an Ilford North constituent and you need my help as your local MP, you should continue to contact my office as normal and my brilliant team of staff will be there to support you.
“But in the meantime I'm going to be following doctors’ orders."
In a tweet Redbridge Council leader Jas Athwal paid tribute to his "dear friend, colleague and inspiration to me for over a decade.
"He's the strongest, most compassionate & dedicated person I know.
"Now is our turn to stand by him & show him the compassion & support he deserves as he has supported so many of us through our darkest days."
John Cryer, Labour MP for Leyton and Wanstead said: "I’m very shocked to hear my friend and colleague Wes Streeting has kidney cancer.
"Sounds like it has been caught early so hopefully he will have a full recovery very soon."
London Mayor Sadiq Khan said he was sending his best for a speedy recovery and was looking forward to seeing him back in action soon.
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