Me and Mrs Jones and Friday Night Dinner are both comedies of domestic life, both of them making an appeal to a sense of shared experience. And one of them works and one of them absolutely doesn't. The one that doesn't is Me and Mrs Jones, which is odd really. It's written by Oriane Messina and Fay Rusling, who have Green Wing and Smack the Pony on their CV, and its comic premise is perfectly workable - a single mother who finds herself falling for her oldest son's best friend. You can play this cross-generational attraction for anguished drama - as ITV's Leaving did recently - but its embarrassments obviously have comic potential too. So why doesn't it bite?

My own explanation would centre on something Gemma's daughter says to her as she drops her off in the playground, after a flustered school run full of slightly effortful blunders: "Stop being a geeky loser." You've hit the nail on the head there, kid, I thought. That, or something like it, is what's written in Gemma's character notes, and it's why we've already had to endure one of those unconvincing scenes in which someone stammers and over-protests after being misheard. Is she really this dim, you think, or is she just written this way? The question doesn't go away as Gemma is forced through a number of over-familiar comic set-pieces - the clumsy answerphone message, agonising over what to wear for a date - all the time behaving not as if she's directed by a recognisable inner psychology but by the need to appear as ditzy as possible. At times, it's desperate, as when Gemma appears from a changing room having tried a dress on over what she's already wearing. Sure. That happens a lot.

Even more problematic is her inconsistency. Gemma is flustered when she really doesn't need to be, but unperturbed when awkwardness might actually make some kind of sense. "Uh! I feel like a teenager on her very first date," she confides, as she gets ready for a night out in front of her son's handsome young friend. A couple of lines later she's blithely explaining to him how she'll use her unshaved legs as contraception. So she's reduced to gibbering silliness by a man she doesn't appear attracted to and coolly overshares with one who notionally has got under her skin. I've never been a single mother in such circumstances, it's true, but I'm still not convinced that's how the world works. The casting doesn't help either. Sarah Alexander looks far too young to be convincing as the mother of a grown-up son and isn't the kind of comedy actress who can finesse the thing into caricature. But the real problem is a script that repeatedly requires her to behave with wild improbability. "I may have slightly over-reacted," she says at one point. Just a bit, Gemma, just a bit.

Meanwhile on BBC One another family based sitcom had just begun, and while this series should be a hit, for some reason it feels a little... drab.

Me and Mrs Jones revolves around divorced mother of three Gemma Jones (Sarah Alexander), who is trying to raise two daughters, while her son has just returned from China to 'find himself'. Gemma not only work and family issues, but also has to deal with her ex-husband Jason (Neil Morrissey), who's now going out with a younger Swedish lady.

In terms of the cast, it looks great. The writers, Oriane Messina and Fay Rusling, worked with Alexander on Smack the Pony and later on one of my favourite shows, Green Wing. And Alexander as well as Morrissey are both established sitcom actors. But I just didn't find this show very funny.

Don't get me wrong, there are some laughs, such as the scene when Morrissey is at a children's football match and celebrates one of his daughters scoring a goal - unaware his face is covered in lipstick. However, most of it felt flat.

It could the fact that I'm familiar with their past work; I was expecting something more surreal and unusual from the writers. Not only was this not surreal enough, it wasn't as grounded in reality as either Friday Night Dinner, which also features a Green Wing actress in the form of Tamsin Greig, or the forthcoming Hebburn.

The show also featured the two daughters vomiting a lot, which was slightly off-putting. Personally, I feel that vomit and 'sick humour' are best applied under the "Elizabeth Mainwaring" rule - it's much funnier when it isn't shown, because the image in your head is much better than the one on screen.

Then again, it could just be that this episode had to follow perhaps the most awkward and unfunny episode of Have I Got News for You there's been in years. So in hindsight, Me and Mrs Jones probably deserves a second chance. Another viewing after a more joyful atmosphere may improve the output. At least I hope so.

This new comedy has such an impressive pedigree (it's written by Green Wing's Oriane Messina and Fay Rusling, and has a pretty strong cast list) that it's almost inevitable that the first episode will disappoint. But give it a chance because it could be a grower, especially among fans of suburban comedies such as the now defunct My Family and Outnumbered.

Sarah Alexander is perfect as the eponymous Mrs Jones, a scatty divorcee with a very modern family life (for which read complicated and messy). Swilling about in the mix of well-intentioned friends and school-age daughters she's got an ex-husband (Neil Morrissey), a grown-up son who returns from his gap year travels with an attractive friend in tow (Misfits' Robert Sheehan) and a handsome admirer (Nathaniel Parker) who the yummy mummies in the playground all fawn over. By the end of the episode she's snogged a man she barely knows and dragged a half-naked one into her bathroom. So which is the "Me" of the title?