Jessica Lee, MP for Erewash and PPS to Dominic Grieve, has become the latest Conservative MP to announce she will be stepping down in 2015.

Many of her colleagues have paid tribute to her abilities, and she will be missed from the Parliamentary party. However, her news will also be seen as a troubling sign of trend: why are female Conservative MPs choosing to leave the Commons?

The uncomfortable fact is that Lee is now the fourth woman MP to announce her departure this Parliament, after Louise Mensch, Lorraine Fullbrook and Laura Sandys.

The response so far has largely been to point out that the majority of those Tories who are stepping down are men. This is true, but a) male MPs are stepping down at a much lower rate, given that they make up almost 85 per cent of the Parliamentary Party, and b) most of those departing are doing so after several terms, whereas all the women who have chosen to leave so far were first elected in 2010.

This now seems to be a distinct problem, not simply a coincidence. My colleague, Andrew Gimson, warned in November that up to a quarter of the newly elected woman MPs might choose not to stand again. With 35 first elected last time round, Lee’s announcement makes it 11 per cent, almost half way to quite a shocking landmark.

Of course, personal circumstances play a major role in most MPs choosing to leave Westminster. Classically, illness and old age take their told on long-serving politicians. In the case of the four female MPs from the new intake, who are much younger than the average departing Member, there may be other personal circumstances in play – Louise Mensch left at least in part because her new husband was based in New York and she wanted to make family life sustainable rather than a trans-Atlantic marathon, for example.

Jessica Lee’s statement attributes her stepping down to personal circumstances of an unknown sort, too:

“I have carefully considered my personal circumstances and responsibilities at this time, before taking this decision.”

Each individual is different, and we should be careful not to ascribe blanket reasons to what are personal decisions, but when 11 per cent of a new generation of female MPs are leaving Parliament after only one term, the Conservative Party ought to scrutinise itself to see if there is something it is doing wrong.

Perhaps, as Andrew suggested, Westminster’s uniquely gruelling form of career hazing is at fault, or perhaps there simply isn’t the right kind of support in place for MPs to sustain personal and family life in the face of their many responsibilities. Alternatively, is there a degree to which the prospect of Parliamentary service held out in candidate selection is simply misleading when compared to the real experience – as business people such as Archie Norman have found out when arriving in Westminster?

At the moment, the advances made in 2010 in terms of better representation of women in Parliament are under threat. Furthermore, with David Cameron already struggling to find sufficient MPs to meet his target for women in the Cabinet, his problems are only going to get worse if more women MPs depart rather than continuing to build up parliamentary and political experience.