Stealthily photographing someone’s knickers might normally get you arrested, but everyone’s at it in the V&A. A ban on photography in the museum’s new exhibition, Undressed: A Brief History of Underwear, means the gallery is full of people furtively trying to snap pictures of pants when the guards aren’t looking. Sneaky museum Instagramming never felt so naughty.

But photography’s not the only no-no in this lineup of lingerie. If you thought you could get away with a quick sketch of that Victorian whalebone corset or the butt-lifting boxers, think again: the museum has introduced a ban on drawing too.

When I tweeted a picture on Thursday of the officious sign that stands at the entrance to the gallery, declaring “No photography or sketching”, it was met with collective grasps of incredulity.

“Is this a late April Fools?” asked one. “How has any artist learned from the past other than through study and facsimile?” Another responded: “No memorising anything you see. Approved memories can be purchased in the gift shop.”

But it transpires that the draconian rule, which was first introduced for the blockbusting David Bowie exhibition in 2013, has nothing to do with protecting intellectual property. A drawing, however realistically executed with the finest charcoal pencil, does not constitute a breach of copyright. Instead, according to a V&A spokesperson, it is to do with preventing congestion and the strict loan agreements the museum signs for each new exhibition.

Allowing students to stand in front of exhibits for hours on end, as they lovingly craft an image of that 1950s Playtex rubber girdle in their sketchbooks, just doesn’t allow the conveyor belt of visitors to flow fast enough. So what next? A ban on wheelchairs and prams because they take up too much space too?

Muscular sinews ... Renaissance statues at the V&A. Photograph: Jean-Pierre Dalbera via Flickr

Having seen the snaking queues that grew outside the museum from 6am every morning for the Bowie show, it’s easy to see why the V&A wants to speed up the flow. But a rule banning sketching goes entirely against everything the institution has ever stood for.

The studious reproduction of museum exhibits has long been a fundamental part of art education – a means of honing drawing skills and offering deeper ways of looking. A visit to the sprawling Victorian repository isn’t complete without clattering into a skinny-jeaned art student poring over their sketchbook, trying to render the muscular sinews of the Borghese Gladiator or capture the intricacies of a baroque fireplace. It is what the V&A has always been about.

There is even a section on the museum’s website extolling the virtues of sketching, summoning the wise words of Le Corbusier. “Drawing in a sketchbook,” he wrote, “teaches first to look, and then to observe and finally perhaps to discover … and it is then that inspiration might come.”

It is particularly untimely for the museum to have introduced the diktat when it is about to unveil an exhibition devoted to the act of copying at the Venice Architecture Biennale. A World of Fragile Parts promises to explore the role of copies as a tool for preservation and to “question the relationship between the copy and the original in a society that privileges authenticity”. Tricky to stage in gallery that forbids copying.

Joyous anarchy ... the vision for V&A East. Photograph: Sam Jacob Studio / V&A

The V&A has been quick to point out that sketching is still welcomed in the rest of the museum, and that the rule only applies to temporary exhibitions, but it still jars with the avowedly accessible ambitions for its new East End outpost. Images unveiled this week suggest the galleries of V&A East, planned to rise from the ashes of the Olympic legacy as part of the new cultural quarter of Olympicopolis, will be a vision of joyous anarchy.

Sam Jacob Studio has conjured up heady scenes of what this “entirely new kind of civic institution” might look like. One space features the Sultan’s elephant careering through the room, on a collision course with a vitrine of knights’ armour, while another level shows the band Nirvana practising in a garage next to Steve Jobs’ nascent workshop, alongside the Rain Room installation – all indicating the kind of creative mix the museum hopes to foster in its new building.

Woe betide anyone who tries to smuggle in a pencil.

