Saudi Arabia has been accused of behaving like Big Brother after introducing technology that alerts male "guardians" by text whenever women under their guardianship leave the country.

The kingdom already bans women from driving and excludes them from most workplaces. It also disapproves of women's sport. Since last week it has been operating a new electronic system that tracks all cross-border movements.

The system functions even if a woman is travelling with her husband or male "guardian", with a text sent immediately to the man. Saudi women must get formal approval from their guardians to travel abroad, and have to hand in an infamous "yellow slip", signed by a male, at the airport or border.

The move has prompted protests. "The new compulsory text service, compliments of the Saudi ministry of interior, is not only a vicious reminder that Big Brother is watching me but that now he will snitch and tell my 'guardian' every time I leave the country," Safa Alahmad, a freelance journalist and documentary maker, said. "Apparently, as a Saudi woman, I don't even deserve the simplest of rights like the right to privacy. The core issue remains the same. Saudi women are viewed and treated as minors by the Saudi government. A text message doesn't change that. It's just adding insult to injury."

"The authorities are using technology to monitor women," the columnist Badriya al-Bashr wrote, criticising the "state of slavery under which [Saudi] women are held".

Some Twitter users compared the Riyadh government to the Taliban. Others jokingly suggested women should be microchipped to keep tabs on them.

Manal al-Sharif, a well-known women's right campaigner, raised the alarm over the new text system on Twitter after a couple alerted her. The husband was travelling with his wife when he received an unprompted text at Riyadh international airport saying she had left the country.

Sharif, 33, attracted global attention last year when she led an underground civil disobedience campaign to allow women to drive. About 100 women took part. Many were arrested and jailed; one was sentenced to 10 lashes, and later reprieved. In June Sharif posted an open letter to King Abdullah appealing again for an end to the ban on women driving, the only law of its kind in the world.

Bloggers in Saudi Arabia have pointed out that the new text system does not merely apply to women. Text messages are also sent to male "guardians" whenever any of their "dependants", deemed to be children of both sexes and foreign workers, leave the country.

The interior ministry introduced the system in April as part of its modernising e-government plan. The goal was to replace the "yellow slip" with electronic permission to leave. The text messages were originally sent to "guardians" who opted into the system, but are now apparently being sent out universally.

According to Human Rights Watch, guardians can include a woman's husband, father, brother or even minor son. They enjoy extraordinary power over female relatives of all ages. They can approve or reject their travel, work, marriages, official business and even healthcare.

Apart from areas such as education and healthcare, women are mostly excluded from the workplace. The labour ministry passed several new decrees in July theoretically increasing the number of jobs available to women. But under pressure from religious conservatives it also restated that strict segregation laws, relaxed in 2005, should apply in the workplace.