JOHANNESBURG (Reuters) - A sudden decision forcing all Congolese nationals to travel on biometric passports from next month has provoked a backlash from lawmakers already vexed by revelations about the documents’ high cost.

FILE PHOTO: An immigration official displays a Congolese biometric passport in the Democratic Republic of Congo's capital Kinshasa, February 10, 2017. REUTERS/Stringer

Even though Democratic Republic of Congo sits near the bottom of the U.N. Human Development Index, the passports it introduced in 2015 are among the world’s most expensive.

A Reuters investigation in April showed that $60 of their $185 purchase price goes to a company registered in the United Arab Emirates whose owner is believed to be a close relative of Congo President Joseph Kabila.

Despite a subsequent outcry, Vice Foreign Minister Aggee Aje Matembo Toto said at the weekend that, from Oct. 16, citizens would no longer be able to use non-biometric passports, some of which are not due to expire until 2020.

Those that tried to would have their document confiscated and replaced with a photocopy, he said in a statement that justified the change on security grounds.

The abrupt ban taps into a climate of political instability fed by militia violence since Kabila last December refused to step down at the end of his mandate.

“Not only is this decision inopportune but it is ...above all unacceptable in the (current) politico-social context,” Zacharie Bababaswe, a deputy from Kabila’s majority coalition wrote in a letter to Aje Matembo Toto.

Opposition lawmaker Juvenal Munubo submitted a formal demand for Aje Matembo Toto to give parliament an explanation. “Aside from the withdrawal of this unpopular decision ... no remedy will be able to reduce tensions,” Munubo wrote on Twitter.

Congolese citizens expressed displeasure on social media, posting under a hashtag translating as: “Don’t touch my passport”.

Reports in the Congolese media and by activist groups about the wealth Kabila has accrued over his 16 years in power have also stoked resentment, while his supporters say he and his family have broken no laws.