The roving member for Shrewsbury, Paul Marsden, was a sewage inspector when he met his wife Shelly, so the odour must have seemed familiar last week when poor Mrs Marsden found an unpleasant surprise on her doorstep: muckrakers from the tabloids, shovelling dirt about her husband — the new Commons lothario.

The bed-hopping, floor-crossing Liberal Democrat was exposed as a “love cheat”, and perhaps more damagingly, a terrible poet. He had enjoyed two affairs while his racy poems were seized upon after, brazenly, he posted them on his website.

Nonetheless, he is still welcome in his marital nest where I meet him — a roomy, swish executive home. An incriminatingly large bunch of lilies jostles with snaps of the happy family. Its vase remains intact but a decorative sword hangs poised over this floral peace offering.

There are few further signs of contrition. Other scandal struck politicians I have interviewed seemed sick with humiliation, but Marsden is chipper. Of my female colleague who fixed this interview, an old acquaintance, he inquired: “Did we ever get it on?” (They didn’t).

He accuses Labour whips — he deserted the party over Afghanistan after a furious row with Hilary Armstrong, chief whip — of leaking his affair as revenge. He says the house is full of coke-snorting, alcohol-soaked, totty-chasing MPs. And after his love poetry, he discloses he has written a novel — with a murder-solving MP for Shrewsbury its hero, and wants the “many” Lib Dem verse-writing MPs to publish a volume of poetry.

The puzzling question is why attractive, apparently clever, young women are keen to enlarge MPs’ majorities. Do they find halitosis and dandruff an aphrodisiac? The Erotic Review sprinkles its list of sexiest men with Gordon Brown and Boris Johnson. And if they are sexy, why not Marsden? Aged 35, he has the libido of Mick Jagger and the face — spookily — of a young Tony Blair. We cannot yet talk of him in the same breath as Steve “Shagger” Norris, but two affairs ain’t bad for starters.

So Marsden, why are you so damned attractive? “MPs tend to be fairly self-confident, good at inter-personal skills, but if you put all 659 in a singles bar and nobody knew who we were, I bet very few would get picked up.” So why is his strike rate so high? “It’s that magnet of power. People act differently. You find reporters and researchers overtly flirt.”

But a backbencher has less power than a Nissan Micra. “Yes, but there is always the possibility of climbing the greasy poll. Someone might say, ‘Have you met Tony Blair?’ and I will say, ‘Yes, I’ve sat across the cabinet table in formal discussions with the guy.’ I know Charles Kennedy: people associated with power, and if that’s what they get off on . . .”

So it’s down to bragging. “Westminster is fabulous if you want to wine and dine someone. It’s easy to sweep someone off their feet; you can show them where Charles I was sentenced to death.” Handy if you fancy necrophiliacs.

It was against the “romantic” setting of Big Ben he first kissed the (so far unnamed) BBC reporter in 2000 that led to a six-month affair. So pick-up wise it beats the Ministry of Sound? “Lots of researchers want to be MPs and will be a little bit loose with their morals. It’s not unknown that because someone has slept with someone they get jobs.” Pause. “It sounds pretty sordid and probably MPs have pretty boring monotonous lives and this is spice that livens it up. I could name a dozen MPs who have had affairs and it hasn’t come out.”

The serpent, he believes, is the sommelier. “It’s usually alcohol to me; I am partial to wine. The culture of the Commons, even now we don’t have late votes, is not to go out. The beer was heavily subsidised and there are 11 bars and restaurants. That’s where the gossip and intrigue is; it’s a magnet to hold you. Some of the scenes I’ve witnessed in Commons bars, my God: MPs blind drunk in various states of undress, being carried into the lobby by ministers. Anyone who says they haven’t seen that is lying.” But surely being drunk and incapable isn’t the most fruitful method to attempt adultery? “You can relax with MPs only so far because there is always some rivalry.” So he sought refuge in a reporter and then Fiona Pinto, who at the time was his researcher, with whom he says a tabloid tried to catch him in a “sting”.

It is easy to see how the sewage inspector turned “quality control manager for a telecoms company” must have felt blown away when, aged 29, he was elected to the Commons in 1997. “I had stayed away from home in places like Slough . . .” he says, trailing off, and one thinks of Ricky Gervais in The Office (set on a Slough trading estate).