Health secretary Jeremy Hunt has written to the government’s senior law officer for “urgent clarification” why two doctors accused of arranging abortions based on the sex of an unborn baby will not face prosecution.

Mr Hunt said abortion on the grounds of gender selection was “against the law and completely unacceptable” and had written to attorney general Dominic Grieve about the decision.

The Crown Prosecution Service decided that although there was enough evidence to justify a prosecution it would not be in the public interest.

The General Medical Council was already involved in the case and had the power to strike doctors off the register, the CPS said.

Director of public prosecutions Keir Starmer said it was “a very difficult and finely balanced decision”, and pledged to reveal more about why the conclusion was reached in due course.

An undercover investigation by the Daily Telegraph involved secretly filming doctors at British clinics agreeing to terminate foetuses because they were either male or female.

Jenny Hopkins, the deputy chief crown prosecutor for CPS London, said the fact that the abortions had not actually taken place influenced the decision not to proceed with a prosecution.

She said: “We have been asked to review two separate allegations against two medical professionals in Birmingham and Manchester concerning requests for an abortion made by a pregnant woman acting on behalf of an investigative journalist.

“Both suspects were doctors and providers of pregnancy terminations at the time of the alleged offences. The undercover operation involved the pregnant woman presenting herself as seeking an abortion on the grounds that she did not want to give birth to a girl. We are satisfied there was no intention to proceed.

“The Abortion Act 1967 allows for an abortion in a limited range of circumstances but not purely on the basis of not wanting a child of a specific gender.

“While the abortions did not take place, attempting to commit a criminal offence - that is, doing something that goes further than just preparing to commit it - is also a crime in its own right under the Criminal Attempts Act 1981.

“Having carefully considered the evidence, we have concluded that although the case is not straightforward, on balance there is enough evidence to justify bringing proceedings for an attempt. Accordingly, we have considered whether a prosecution is required in the public interest.

“One highly relevant factor in this regard is that the responsible professional body, in this case the General Medical Council, is already involved and has the power to remove doctors from the medical register.

“Taking into account the need for professional judgement which deals firmly with wrongdoing, while not deterring other doctors from carrying out legitimate and medically justified abortions, we have concluded that the cases would be better dealt with by the GMC rather than by prosecution.

“In coming to this conclusion, we have also taken into account that in these cases no abortion took place or would have taken place.”

Mr Hunt voiced concern about the decision and demanded clarification about the grounds on which the CPS reached it.

He said: “We are clear that gender selection abortion is against the law and completely unacceptable. This is a concerning development and I have written to the attorney general to ask for urgent clarification on the grounds for this decision.”

Mr Starmer said the decision was taken on the facts of the case and did not reflect a more general policy.

He said. “This was a very difficult and finely balanced decision. It was based on the individual facts of the case; it is not a policy decision.

“But in light of concerns raised today, I have decided that it would be sensible to put into the public domain the case specific reasons for not prosecuting in much greater detail.

“Clearly this will involve careful consideration of how much information can be put into the public domain by way of explanation, but my intention is for a fuller statement to made by the CPS in due course.

“In the meantime, I understand that the health secretary has written to the attorney general asking for clarification and I am happy to assist him in any way.”