Joined the Conservative Party aged 18 and went on to contest the Wolverhampton North East seat at the 2001 general election. Became MP for Basingstoke in 2005. Later that year she was appointed shadow minister for education before taking up her current portfolio.
WHAT IS HER BACKGROUND?
Brought up in South Wales, Miller went to a comprehensive school in Bridgend and studied economics at the London School of Economics. She then worked in PR and marketing for Texaco before moving into politics full-time. She has been married to solicitor Iain Miller since 1985.
WHERE DOES SHE SIT POLITICALLY?
Ardently opposes the new EU constitution and entry into the single currency. She appeals to Conservative hardliners with her calls for more police and firmer sentencing guidelines.
WHY IS SHE A WOMAN TO WATCH?
Miller is thought to be living proof of Cameron's pledge to promote more women in the party, having risen through the shadow cabinet. Cameron is said to see her as a possible future chancellor.
THINGS YOU MIGHT NOT KNOW
Miller opposes gender-based candidate selection. 'I don't want all-women anything, I want the best candidate,' she once said.