Heidi Alexander has been appointed shadow health secretary by the new Labour leader Jeremy Corbyn.
The announcement follows the election of Mr Corbyn, the veteran leftwing MP, as Labour leader in a landslide victory on Saturday.
The previous shadow health secretary and leadership contender, Andy Burnham, is to be shadow home secretary.
Ms Alexander has been the MP for Lewisham East since 2010. It is her first shadow cabinet position, although she has served as a Labour whip since March 2013.
She supported Mr Burnham’s Labour leadership campaigns in 2015 and 2010. Ms Alexander was also a vocal campaigner against the last government’s attempt to downgrade Lewisham Hospital.
Ms Alexander tweeted yesterday that she was “humbled to serve as shadow health secretary”.
“The NHS is facing immense challenges and I will do all I can to hold this government to account,” she added.
In his commencement speech on Saturday, Mr Corbyn hinted that it would be Labour policy to end the NHS purchaser-provider split in England.
Praising Welsh Labour, he said: “I congratulate them on ending the internal market in the health service in Wales, something we want to do in the rest of Britain.”
Another health priority for Mr Corbyn is likely to be private finance initiative debt.
Last month he wrote a column in The Guardian, arguing that Labour should “campaign for a fund to be set up to bail out NHS trusts from PFI schemes forced upon them”.
The news of Mr Corbyn’s victory was greeted by the immediate resignation of shadow health minister, Jamie Reed.
In his resignation letter he wrote: “No amount of well meaning protest will protect the NHS, drive up standards, recruit more medical professionals or improve the accessibility of world class health care to the British people. Only an elected Labour government will do this.”