A leaflet from a firm shortlisted for the Oxfordshire Business of the Year award was sexist and offensive, a watchdog group has ruled.

Digital Workshop, in North Bar, Banbury, sent customers a mailshot featuring pictures of a scantily clad woman inviting clients to "get a bigger slice of the tart". It was promoting computer software.

It prompted one woman to complain to the Advertising Standards Authority (ASA), claiming it was gratuitous, sexist and offensive. Her criticism was upheld.

The four-page advert pictured a girl lying on her back wearing a slip which only just covered her thighs.

The copy said: "Take full advantage. . . of our NO RISK trial offer", and "get more action - captivate them - keep them interested - do it like a pro!"

The firm's media communications manager, Bree O'Mara,told the ASA that the leaflet, distributed to 5,000 male customers, was deliberately tongue in cheek.

She added that the word tart was a play on words designed to appeal to people who worked with pie-charts.

The ASA said it had not only been distributed to men and that, even if it had, many of them might have found the "language and imagery gratuitous and sexist".

Digital Workshop designs educational programmes for schools and universities and was shortlisted in April for a Business of the Year innovation award.

Ms O'Mara said the firm regretted the campaign: "We were acting on the advice of our business development manager, who has now left us," she said.