Clegg will hope Sarah Teather's is an isolated case

It won't be so easily dismissed if any other sitting MPs walk away

Teather: Something ‘did break for me’ when party backed benefits cap (PA)

So Sarah Teather has decided she has had enough of being a Lib Dem MP and is standing down at the next general election.

For Teather-watchers (a select breed who have too much time on our hands) this does not come as a huge surprise. She has clearly been very unhappy since she lost her ministerial position last year in favour of David Laws and has made numerous comments critical of the government. Indeed in her resignation interview she talks about feeling "depression" at some of the actions of the party in government.

I am sure many Lib Dem activists will sympathise with Ms Teather's plight and wish her well. However there is a significant group of party members who will never forgive her for her actions over the equal marriage bill, which she voted against back in February. She published a somewhat rambling and incoherent justification of this decision, claiming the bill would "make family life more unstable", which really only had the effect of enraging activists further. There is some suspicion among members that the aftermath of that decision could be at least partially behind Sarah's decision to stand down. A great many of the activists who helped her get elected in a stunning by-election victory in 2003 and in the subsequent general elections are the same people who felt so betrayed - and would find it very hard to campaign for her in 2015.

Equal marriage aside, Sarah's record in parliament has generally been good from a liberal perspective. She has been a tireless campaigner on immigration and the rights of migrants. She even managed to secure the release of one of her constituents from Guantanamo Bay, which she rightly claims is one of the highlights of her career. She also steered the pupil premium through government as the minister responsible.

Of course when in government she had to vote for things like tuition fees - but it is probably unfair to single her out for criticism in this respect. Where criticism can more fairly be levelled at her however is over the issue of why she did not resign before being pushed in 2012, as her statements since have made it abundantly clear she was very unhappy in government. It was ever thus though for ambitious politicians wanting to make their mark. Perhaps what is surprising these days is that it is Lib Dem MPs having to make these sacrifices, something which as a party we are not used to.

Her valedictory comments about the party in government and Nick Clegg in particular will strike a chord with many party members. The benefits cap, the £1,000 immigrant deposit, secret courts and many other policies that have been either announced or brought in have left the party at large feeling battered and bruised. There is an increasing disconnect between what the party reps have voted for at conference and what is happening in government. There were always going to have to be compromises but what Teather's resignation underlines is the widespread view that in too many cases the wrong compromises have been made.

One other factor that should not be forgotten is that Sarah Teather is one of only seven female MPs (out of 57 in total) that the Lib Dems have. Whichever way you look at it this is a blow to the party's gender balance ambitions. There are however many good aspiring female candidates within the ranks of members, some of whom have already been selected for winnable seats for 2015.

I suspect that this announcement will largely be brushed off by the party leadership. It is easy to characterise Teather's resignation as sour grapes for having lost ministerial office and fear of losing her seat, due to her own actions on equal marriage. But it is more complicated than that and what Clegg and his advisors will be hoping is that this is an isolated case. It won't be as easy to dismiss if any other sitting MPs way-off retirement age start to announce they have also had enough.