LONDON, Jan 22 (Reuters) - Fashion retailer H&M has withdrawn an ad featuring school girls after complaints that the campaign encouraged the sexualisation of under-age girls.

The advert, launched in Australia, featured the slogan: "Make those heads turn in H&M's Back to School fashion" above a photo of two girls wearing gray H&M pinafore dresses.

"We have removed this ad," an H&M spokesperson said on Monday. "We are deeply sorry for the offence this has caused and we are looking into how we present campaigns going forward."

The fashion retailer's shares hit a two-month low, down 1.4% by 1540 GMT, underperforming peers.

H&M's rowback is the latest in a string of missteps by fashion brands leading to adverts backfiring. In December, Zara pulled a campaign featuring statues wrapped in white, after calls for a boycott and protests over a perceived resemblance to images from the war in Gaza. (Reporting by Helen Reid. Editing by Jane Merriman)