In the mainly Muslim and deeply conservative country, where dating is discouraged, parents complained to the telecoms regulator, the Telecommunications Regulatory Commission (BTRC), that the free night calls were changing their children's behaviour.

"The commission has taken the decision following a flurry of complaints by parents against such free late-night facilities," a commission official said on Monday.

The move has not gone down well with the young. "Such an order is shocking and surprising," said university student Kaushik Ahmed, in Dhaka. "Parents should be able to build up their children properly and inject values in them before turning to telecom regulators to shape their lives."

Two of Bangladesh's five mobile phone firms - GrameenPhone, a unit of Norway's Telenor, and CityCell, a venture between SingTel and Bangladesh Telecom - offer the free calls between midnight and 6am to attract the active youth market.

"We are surprised to receive such a letter from BTRC because the customers benefit from increased competition," said Syed Yamin Bakht, general manager of market leader GrameenPhone.

As in many developing nations, mobile phone services are taking off rapidly, far outstripping landlines. Bangladesh, with a population of 140 million, has 9 million mobile phone users - a figure expected to double to 18 million this year. There are one million fixed-line phones.