The Crown Prosecution Service's failure to take action in recent cases of sex selection abortions has been criticised by the Christian Medical Fellowship (CMF).

CMF said the decision had effectively legalised the practice in Britain and raised serious questions about the role of the Crown Prosecution Service (CPS) in upholding the law.

The Metropolitan Police said in a letter to CMF that although there was sufficient evidence to convict two doctors involved, the CPS believes it is not in the public interest to prosecute.

An undercover investigation by the Daily Telegraph secretly filmed Dr Raj Mohan and consultant Prabha Sivaraman agreeing to arrange terminations for a pregnant woman who said she did not want to go ahead with the pregnancy because of the sex of the unborn child.

With regard to doctors at 14 NHS Trusts who pre-signed abortion forms authorising abortions for women they had not actually seen, the CPS has also opted not to act on grounds that "the practice of pre-signing has clearly evolved over a number of years", is "clearly widespread" and may well be due to "clinical pressures" or "good intention".

Dr Peter Saunders, chief executive of the Christian Medical Fellowship, said authorising abortions purely on grounds of sex selection and pre-signing abortion authorisation forms were both "flagrant breaches" of the Abortion Act.

"The unwillingness of the CPS to act in these cases after an investigation spanning 18 months is quite extraordinary," he said.

"It sends a strong signal that sex selection abortions are now effectively legal in Britain, rubber stamps the practice of pre-signing and gives a green light to doctors to interpret the abortion law as they see fit in the knowledge that the authorities will turn a blind eye.

'Knowingly and wilfully making false statements on statutory documents – which is what abortion authorisation forms are – is actually a form of perjury. But we seem to have reached a point where, at the whim of the CPS, clear statutory procedures can be disregarded by doctors and NHS Trusts without any fear of legal repercussions.

"This puts doctors above the law and raises serious questions about the role of the CPS in upholding the will of parliament."

Dr Saunders called for an "urgent investigation", adding that CMF was seeking legal advice on the matter.

Andrea Minichiello Williams, chief executive of the Christian Legal Centre, said the CPS was "abdicating from its responsibility to make sure the law is kept".

"This is contrary to the law. Parliament makes the law and the CPS should enforce it," she said.

"Its actions communicate that sex selection abortions are practically legal – something the vast majority of Britons would find reprehensible.

"We believe in the rule of law and that girls should not be terminated because boys are wanted.

"We shall be seeking counsel's opinion and are considering a judicial review of this decision."