Do you think my bum looks big enough in this?

It seems it's not a question of "does my bum look big in this?" any more - rather "does my bum look big enough in this?" And it's not just Jennifer Lopez and Kylie Minogue who appear to have signs of surgical enhancement in the quest for the perfectly rounded posterior.

J-Lo may be one thing - Latinos are renowned for their love of big bottoms - but why is it that British women suddenly want fuller behinds when until now we've hated the idea that our backsides might look big at all?

Top British cosmetic surgeon Laurence Kirwan - who practises in Harley Street and Connecticut - believes that our obsession with the small, pert bottom is over and interest in the more exotic shape, beloved by South Americans, is finally getting to us.

"Traditionally, a British woman's ideal shape perceived by both sexes is large breasts, slim hips and buttocks. The Hispanic Jennifer Lopez type is totally the reverse: smaller breasts, very ample, round bottom.

"London women seem to be looking for more curves. They may already have a lovely butt that's the envy of their friends, but now they want it more so."

Despite the rumour that our celebrity bottom tweakers may have had buttock implants, there are more subtle - and less hazardous - ways of giving one's buttocks a little something to add fullness and shape. Kirwan, for instance, has perfected "bottom-shaping" procedures for London women who want a boost and, he says, more fat is the answer, not silicone.

"I don't like - and don't do - buttock implants. It will never become as fashionable as the breast implant. It's a nasty business, fraught with potential risks and complications. The fat transfer is much more preferable - fat is taken by liposuction from the thighs, stomach or hips and put in the buttocks.

"The great thing about fat injections is that fat is 'material' from your own body. The only problem with this procedure is that whether most of the fat 'lives' or gets lost by disappearing back into the system depends on the individual's metabolism. But when this really works it is brilliant because the effect lasts virtually permanently. I take 200-300cc of fat from, say, each thigh and distribute it in a fan shape all around each cheek. In a good case, about half

that volume will be lost but enough remains to keep the shape. Liposuction is expensive at £2,000 minimum but I don't charge to inject the fat back into the bottom. After all, it's the patient's own material!"

However, Kirwan predicts the next big trend in cosmetic surgery will be " bodylifting" which has become increasingly common among American women.

Stand sideways, naked, in front of the mirror, grab the skin on one side of your hips, pulling it upwards, and you'll get the idea ... nice, tight thighs and buttocks.

"The 'lower body-lift' is particularly good to rectify the downward slide in older women," says Kirwan. "It also works well on younger women who have lost a lot of weight resulting in sagging skin. It's radical but the most effective procedure; we trim about six inches of skin and fat away from the thighs and hips, so there's some fat to pop into the buttocks for good measure. The scar runs from each side of the groin to the midline of the back, the operation costs around £10,000 and recovery takes two weeks as it's pretty painful - but the results are great."

If it's simply a J-Lo bum you're after, then a cheaper option, the £4,000 " Pitanguy Lift" - named after the Brazilian surgeon who invented it - could be the answer. Skin folds at the nether end of the buttock are pulled down and removed, giving a rounded, taut curve to the cheeks. "Again, this can be done in combination with fat injections to plump out the area," says Kirwan.

The downside is that because the scars are in the crease under your cheeks, you can't sit on them for a good 10 days afterwards, so have to stand or lie on your side or stomach. But for those determined to have a perfect posterior, this has to be a small price to pay ...

? Laurence Kirwan, 10 Harley Street, W1, 0207 467 8559, www.drkirwan.com