Image caption The dinner table conjures up a potent array of imagery for politicians

Hostility to Muslims has "passed the dinner table test", a peer claims. So how did this item of furniture become the benchmark for what is and isn't acceptable to say?

You start with the cutlery on the outside and work your way in. The port is passed from right to left and you never, ever, blow your nose on the napkin.

To the socially gauche, meal-time manners are already baffling enough. And now it appears that, all along, an unwritten code has governed the opinions we express while sitting down to eat.

In a speech, Baroness Warsi, co-chairman of the Tory Party, is expected to warn that prejudice towards Muslims had "passed the dinner table test" and become socially acceptable.

Her remarks are no doubt designed to provoke a debate about tolerance and mutual respect within a multicultural society. But, intriguingly, they also suggest that prandial protocol is governed by a strict set of rules about discussing controversial issues.

Just as the water cooler is associated with gossip or chats about last night's television, the dinner table has certain assumed conversational rules of engagement; don't upset Auntie Margaret by talking about Uncle Ian's first marriage, for instance.

It also, too, carries with it associations of a cosy evening among friends or the "hard-working families" so often invoked by MPs.

Indeed, this is not the first occasion that a British centre-right politician has invoked such imagery.

You don't talk about religion, sex or money at dinner Simon Fanshawe, Etiquette expert

During his time as Tory party leader, William Hague staked out a claim for his own brand of "kitchen table Conservatism" - to the extent, according to contemporary reports, of installing an actual wooden table at the heart of his party's headquarters to act as a reminder to staffers how swing voters might sit down to their chicken Kievs.

In the most recent case, the meal-time analogy is used to make a point about the limits of polite discourse. The etiquette expert Simon Fanshawe says he agrees with Baroness Warsi that such occasions imply a level of conversational civility.

"I love a good argument, but I never let people bring up Iraq at my dinner table - it simply descends into a toxic row," he says.

"It all comes back to the old rule that you don't talk about religion, sex or money at dinner.

"Essentially, eating together isn't about the food, it's about the common experience - that's why you wait for each other before you start, that's why you don't leave the TV on. Then you combine that with the British terror of conflict - it's about avoiding feeling uncomfortable."

However, not everyone is so appreciative of Baroness Warsi's rhetorical device.

The Times food critic Giles Coren argues that the dining table is most commonly used by politicians to hark back to a mythic bygone age of nuclear families.

Image caption Baroness Warsi said she was speaking out as part of an "ongoing battle against bigotry" Muslim prejudice 'seen as normal' - Warsi

Moreover, he insists, it is fetishised via dinner parties by those least likely to express an aversion to any minority group.

"It has these north London, Islington connotations, when in fact those sort of people would be desperate to have a Muslim or a black person or a homosexual at their dinner table to show how inclusive they are," he says.

"I think she wants some Jamie Oliver cred. But we're always being told we don't sit down for dinner together enough.

"Because eating and drinking is something that we all have in common, politicians think talking about it will make them look normal."

It is a charge that surely would be rejected by Baroness Warsi, who was reared in the distinctly un-metropolitan environs of Dewsbury, west Yorkshire, of working-class stock.

But the writer and restaurant critic Zoe Williams insists that the kind of meals attended by a front-rank politician have very different social rules from those experienced by most of the population.

"If you're at a dinner party and you're sat next to Michael Gove, it's a very, very active social test," she says. "You're expected to be provocative - it's like going on the Late Review."

Lexicographers will be alert to whether Warsi's phrase catches on. In the meantime, the social obstacle confronted at dinner tables by most of us surely will be remembering to keep our elbows off them.