Rafael Nadal has threatened to take legal action against former French health and sport minister Roselyn Bachelot after being accused of failing a test for performance enhancing drugs which led to his seven-month spell out of the sport.

The allegations come in the wake of the revelation that former world number one Maria Sharapova faces a ban from the sport after admitting to taking a banned substance.

Nadal had attributed his absence at the back end of 2012 and the start of 2013 to a long-standing knee problem which forced him to miss two grand slams and the Olympic Games. The Spaniard has been dogged by such issues throughout his career but has still been able to claim 14 grand slam titles, including nine at the French Open.

Last week, Bachelot who served on former president Nicolas Sarkozy's cabinet and is a trained pharmacist, claimed the actual reason for Nadal's lengthy absence from the sport was due to him having been banned for taking a banned substance. "We know that the famous injury which kept Nadal out for seven months is without any doubt because he tested positive," she told Canal+. "When you see a tennis player out of action for a long time, it's usually because they've tested positive."

The former world number one has never tested positive for performance-enhancing drugs and has therefore reacted angrily to the accusations – threatening to sue Bachelot and anyone else who repeats the allegations. "There is a couple of times I heard comments like this, and that's what – this gonna be the last one, because I gonna sue her," he said after his second round win over Giles Muller at Indian Wells.

"I am tired about these things. I let it go a few times in the past. Not more you know. I know how tough I worked to be here. To listen, to heard those comments from a person that should be serious, because was minister of a big country and a great country like France. So I gonna sue her, and I gonna sue everyone who gonna comments something similar in the future, because I am tired of that."

The 29-year-old, now fifth in the ATP rankings, added: "A minister of France should be serious. This time is the time to go against her. We gonna sue her, and since the day after day I tell you that everyone who has another comment in this way gone happen the same, because that's too much for me."