Mexico is bracing itself for communications chaos tomorrow, with some 24m mobile phone lines due to be disconnected as part of a government crackdown on organised crime.

The government announced today that only around 71% of the 83.5m mobile lines in Mexico had been logged with a new register, and that the disconnection of the rest was set to begin.

The register was designed to help combat the use of mobiles in crimes such as kidnapping and phone extortions threatening violence unless the victim hands over some cash. But confusion and organisational disarray have marred the plan.

Despite plenty of coverage of the issue in the press in the last few weeks, many Mexicans were unaware of an obligation to submit their data before the deadline of midnight on Saturday, or they simply failed to get around to registering.

Some mobile phone owners also refused to send the required text message with their personal information on the grounds that they saw the register as an affront to their civil liberties .

"I didn't register mine because I don't trust the government," said one student, César Correa as he hurried along a Mexico City avenue. "They say it is for our security but I believe it is a measure to control society."

Others pointed out that criminals could easily get around the new controls, either by using stolen phones or registering their own using different identities.

"It is pointless," said a hospital porter, Gerardo Morales, who nevertheless submitted his data for fear of being left without communication. "Protesting against it is pointless, too."

As the deadline approached, Facebook and Twitter communities encouraged each other to register their phones with the data of public figures ranging from the president, Felipe Calderón, to the world's richest man, Carlos Slim, who owns the biggest mobile company.

A month ago, the daily newspaper Reforma received confirmation for several phones it registered using the data of the national head of public security, Genaro García Luna.

Héctor Osuna, the head of the telecommunications regulator, insisted the information would be used for no purpose other than safeguarding user security. "We will be the only ones who have access to the information," he said on the main breakfast TV show today.

Actually disconnecting the phones is the responsibility of the mobile phone companies, and these may prove reluctant to carry out a government order that means they suddenly lose millions of customers.

Slim's company América Móvil unsuccessfully lobbied for an extension of the deadline. And last week Móvistar, a subsidiary of the Spanish telecoms giant Telefónica, threatened to ignore the government's order altogether.