In a letter to Prime Minister Rishi Sunak on 24 May, the South Northamptonshire MP said she had decided to stand down after ‘careful reflection'.
Leadsom, who has held a number of Government position during her 14 years an MP, said her ‘greatest passion' was ‘seeking to support every family to give their baby the best start for life'.
She said: ‘It is here, in the period between pregnancy and the age of two, the 1,001 critical days, when the building blocks for lifelong emotional and physical wellbeing are laid down. I hope and pray that the next Government will take forward this work to change our society for the better.'
Listing her achievements as junior health minister, Leadsom cited rolling out the Family Hubs and Start for Life programme, dental contract reform, providing support for GPs and the Smoke Free Generation Bill.