Alison Saunders, the director of public prosecutions, has defended her decision to bring Britain’s first FGM case against a doctor who was cleared of committing the crime on a woman he stitched after the birth of a child.

A leading hospital consultant has accused the prosecution of being ludicrous after a jury took less than 30 minutes to clear Dr Dhanuson Dharmasena. The woman had been subject to FGM aged six in Somalia and the doctor was accused of reinstituting it.

Dr Katrina Erskine, consultant in obstetrics and gynaecology at the Homerton hospital in London, said she was left with no faith in British justice.

But Saunders told BBC Radio 4 there was enough evidence for it to go to court. She said the case had been reviewed thoroughly and a judge had agreed that the evidence should be heard despite three attempts by the defence to have it thrown out.

“I think the spirit of the legislation is that FGM, whoever it is committed by, is an offence,” she said. “It is a crime and there are exceptions if it is necessary for a woman’s mental or physical health but, of course that is a question which is in itself right to put before a jury.” Saunders said the verdict did not make her stop and think.

She said the Crown Prosecution Service only had to pass a threshold of having “sufficient evidence for a realistic prospect of prosecution” whereas a jury needs to be satisfied beyond reasonable doubt.

The authorities have been under pressure to find a case of FGM to prosecute amid reports that thousands of girls in Britain have been cut and none of the perpetrators brought to justice.

In an interview with the Guardian, Erskine said: “It is ludicrous to conflate anything a doctor or midwife may do at the time of delivery to a woman who has already suffered FGM with FGM itself, and it is insulting to women who have actually suffered FGM.

“It is also a diversion from what we should really be addressing, which is to try and find a way to reduce the incidence not just for girls born in the UK but worldwide.”

After a two-and-a-half-week trial at Southwark crown court, a jury cleared Dharmasena of carrying out FGM on a woman after delivering her first baby at the Whittington hospital in London in November 2012.

The woman had been subjected to FGM aged six in Somalia and the doctor was accused by the crown of stitching her up after childbirth in a way which reinstituted her FGM.

Speaking after the acquittal, Dharmasena, who has received death threats and is suspended from the medical register, said: “I am grateful to the jury for their careful consideration of the facts.

“I have always maintained that FGM is an abhorrent practice that has no medical justification… I would like to thank my family, friends, legal team and all those who supported me through this difficult time and I look forward to putting this matter behind me.”

The prosecution of Dharmasena was announced by Saunders in March last year. It came after growing political and public pressure on police and prosecutors – including an inquiry set up by the home affairs select committee – questioning the failure to bring a single prosecution for FGM in this country since 1985.

Dharmasena told Southwark crown court during his trial he had acted at all times in the best interests of the patient to stem bleeding following an incision he made during labour to allow the baby to be born safely.

Erskine – who is an expert on working with women who have suffered FGM – questioned the timing of the DPP’s announcement of the charge last year. “It was very interesting that the prosecution got announced three days before the director of public prosecutions was called before the select committee,” she said.

“I think they [the CPS] were responding to a lot of public pressure. I find myself wondering how far I should go to say that FGM is the slicing off on a conscious young girl with no anaesthetic of her clitoris and labia...

“This is a quibble about a couple of stitches and it is a complete distraction.”

Mr Justice Sweeney, in summing up to the jury on Wednesday, said everyone accepted Dharmasena had saved the life of the woman’s baby in an emergency delivery on 24 November 2012.

The doctor, he told the jury, had been let down by “systemic failures” at the Whittington hospital, which meant the woman had not been picked up during antenatal appointments and sent down the FGM pathway to be seen by a consultant and a specialist team weeks before she went into labour.

Instead she presented in labour and Dharmasena, the on-call registrar, had to delivery the baby in an emergency procedure which involved him making a cut through the scar tissue of her FGM. The crown claimed the 1.5cm stitch he had used afterwards to repair the scar amounted to reinstituting the FGM, and was a criminal offence.

Dharmasena told the jury he had used the stitch to stem the bleeding which AB, the patient, was suffering following the cut and her childbirth. “I decided to put in a suture to stop the bleeding,” he said.

During the trial process the judge rejected two attempts by the defence to dismiss the prosecution on the grounds that, under the Female Genital Mutilation Act 2003, a doctor is exempt from prosecution if a surgical procedure was carried out on a woman in labour or after childbirth and was medically necessary.

The doctor, who qualified in 2005 and began specialising in obstetrics and gynaecology in 2008, had joined the Whittington hospital in London some six weeks before the incident in November 2012.

He said he had not had training in FGM during his undergraduate medical degree, or his postgraduate studies. He also admitted he had not read the hospital policy on FGM.

In a statement, the Royal College of Obstetrics and Gynaecology said: “This case highlights the complex issues around the care of female survivors of FGM and the resource implications for NHS services, including early identification and referral.

“It demonstrates the difficulties and pressures that trainee doctors face in busy labour wards in the immediate postpartum period. It is vitally important for all clinicians to ensure that they are aware of the law and of the relevant guidance from their professional bodies in fulfilling their roles and responsibilities.

“Similarly, it is also important to distinguish between FGM/re-infibulation and medically-indicated surgical procedures to correct trauma such as the stitching of perineal or labial tears following labour.”

Hasan Mohamed, who was charged with aiding and abetting the doctor, was also acquitted.