A French judge has ordered that the phone of former President Nicholas Sarkozy be tapped as part of a probe on whether he took funds from ex-Libyan leader Colonel Gaddafi to help bankroll his 2007 election campaign, the French daily Le Monde reported.

The judge allegedly first ordered Sarkozy's phone be tapped in April 2013, as well as the phones of two of his former ministers, Brice Hortefeux and Claude Gueant, the paper revealed Friday.

But someone involved in the investigation most likely tipped Sarkozy off, as he became extremely careful about using his official phone. He and his lawyer then acquired secret mobile phones, the paper claimed. Investigators eventually found out about them and ordered they also be bugged.

Last year, French judges launched an investigation over allegations that deposed Libyan leader Muammar Gadaffi gave money to Sarkozy's 2007 presidential election campaign. The explosive allegation first emerged in 2011, after Sarkozy played a central role in ordering French armed forces to help topple Gadaffi's regime.

Saif al-Islam, one of Gadaffi's sons, claimed Libya helped finance the French president's election campaign. In an interview with Euronews TV channel, Saif threatened to make public the details of the bank transfers after France played such an instrumental role in toppling his father. He also demanded that the French president return the money.

Sarkozy is suspected of rigging a settlement procedure to make sure Tapie got the cash as a 'thank you' for supporting him in the 2007 election. Tapie already has several corruption convictions, including one for match fixing when he was boss of Olympique Marseille football club.

READ MORE: Sarkozy’s phone ‘tapped’ over Libya cash claims