Several leading members of France's right-wing opposition, itself reeling from a string of corruption cases allegedly implicating Sarkozy and several others, have called for the resignation of Justice Minister Christiane Taubira over the affair.
The scandal centres on explosive revelations on Friday that Sarkozy is being probed over suspicions he attempted to pervert the course of justice by trying to obtain secret information about an ongoing court case from a friendly judge.
The phone-tapping revelations -- a first for a former president -- caused outrage among Sarkozy's supporters and the focus soon shifted on to whether the Socialist government knew about the taps amid concerns the constitutional separation of powers had been breached.
On Monday, Taubira said she had no prior knowledge of the phone taps and had learnt about them at the same time as the French public.
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Jean-Francois Cope, the head of the main opposition UMP party, slammed the phone-tapping as "political espionage", labelling it an "affair of state".
The justice minister "lied" and "it's not possible for her to stay in her post. Her resignation over this lie is inevitable," Cope said yesterday.
Just 10 days ago, Cope himself was under fire following press revelations that lucrative contracts given out by the UMP party benefited people close to him.
Meanwhile Alain Vidalies, the Socialist minister in charge of government relations with parliament, lashed out at the UMP for what he labelled "a successful smokescreen.