The 47-year-old denies the allegation and has avoided extradition to Sweden to face the charge for seven years after seeking refuge at the Ecuadorean embassy in London in 2012.

He is currently being held at the high security Belmarsh prison since Ecuador withdrew asylum last month after which he was sentenced to 50 weeks in jail for failure to surrender to meet his bail conditions.

The Swedish authorities had originally decided to drop the rape investigation two years ago, saying they felt unable to take the case forward while Assange remained holed up inside the Ecuadorean embassy.

"I have today taken the decision to reopen the prelminary investigation,” Eva-Marie Persson, the Deputy Director of Public Prosecutions, told reporters on Monday.

A lawyer for one of the women involved in the Swedish allegations subsequently asked for the investigation to be resumed. Assange had also faced an investigation over a second sex-related allegation, but this was dropped in 2015 because time had run out. He has denied both allegations.

Assange unsuccessfully fought in the British courts to have the Swedish extradition order and preliminary investigation dropped. His lawyers said he feared that should he go to Sweden, authorities could hand him over to the US to face prosecution over the WikiLeaks case.

WikiLeaks said the reopening of the Swedish investigation would give Assange a chance to clear his name.

"Since Julian Assange was arrested on 11 April 2019 there has been considerable political pressure on Sweden to reopen their investigation, but there has always been political pressure surrounding this case," Kristinn Hrafnsson, WikiLeaks' editor-in-chief, said in a statement.

"Its reopening will give Julian a chance to clear his name," it added.

The decision to reopen the inquiry is likely to raise the question of which extradition request should take precedence: that of Sweden or the US.

The US wants to extradite Assange from the UK over his alleged role in the release of classified military and diplomatic material in 2010.

Australian-born Assange faces a charge of conspiracy to commit computer intrusion in the US. He is accused of participating in one of the largest ever leaks of government secrets, which could result in a prison term of up to five years.