Corrupt women government officials are increasingly using beauty salons to cover their tracks, prosecutors and legal experts said.

Since March last year, Beijing's prosecuting authority has handled 13 cases of bribery or misuse of public funds involving spas.

Twelve of these suspects were women, mostly high-level officials, according to Wu Min, a news officer at Beijing No 1 People's Procuratorate.

The defendants were all accused of accepting membership cards to beauty salons as bribes or abusing their position and using taxpayers' money to cover the cost of treatments.

"This kind of corruption has become prominent in recent years," Wu said.

In December last year, Bai Hong, former chairwoman of the labor union at Beijing Municipal Health Bureau, was sentenced to 15 years in prison for appropriating almost 4 million yuan ($642,000) of public money for facial and body treatments.

From July 2006 to March 2011, she used cash and checks from the bureau at a beauty salon.

Wu said authorities were tipped off by an anonymous letter, and that Bai was the first woman official in Beijing to receive a criminal sentence for corruption involving a spa.

"The average age span of women officials involved is from 40 to 50, and most were from government administrations or large enterprises," Wu said. "Women love beauty treatments, and female officials tend to pay a lot of attention to their image."

Yi Shenghua, a lawyer with about 10 years' experience in criminal law, recently defended an official accused of spending public money on spa treatments.

"It's become common since 2000, when there was a boom in salons," he said.

The woman he defended, who lost her case, "thought it was her bonus for working hard, and also didn't believe she'd be discovered", Yi said.

Zhu Lijia, a professor at the Chinese Academy of Governance, said the nature of the crime is the same, no matter what corrupt ways officials use.

He added that the key to the problem still lies in transparent government supervision.

"We can't blame the salon or the spa. They're just the place where the money is spent," he said.

Zhou Liwen, a prosecutor in Changsha, Hunan province, said bribery with membership cards for beauty shops is also common in his city.

"Each official in our city has a card for paying public expenses during business trips and other activities, which is supervised by the local financial bureau," he said. "If officials' spending cannot match items on budget lists and shows extra costs, they will be under investigation and punished if the circumstance is serious."