Dame Tessa Jowell is battling with brain cancer, her family has revealed.
The former culture secretary and Labour peer tweeted: "Thank you for so much love and support on my birthday.
"More people living longer better lives with cancer is my birthday pledge."
Ms Jowell, 70, posted the message alongside a picture of her family.
She stood down as the MP for Dulwich and West Norwood at the 2015 general election, after a long career in politics, including leading London's bid to host the 2012 Olympics under former prime minister Tony Blair.
Her daughter-in-law, Ella Mills, a food blogger known as Deliciously Ella, wrote on Instagram that she was inspired by Ms Jowell.
"The last few months have been some of the hardest of our lives, after Matt's Mum was suddenly diagnosed with brain cancer in May.
“Her bravery, optimism, love and support for others during this process has inspired us both so much, and today, on her 70th birthday, we're all pledging to try and do everything we can to make people's lives with cancer better for longer.
“I'm sure so many of you have had to deal with this process too, and Matt and I will work to find new ways of supporting and enhancing people's lives who have been affected.”
The social media posts from Ms Jowell and Ms Mills are the first time any of the family have spoken publicly about Ms Jowell's illness.
