The Attorney General has said a former religious studies teacher's sentence cannot be referred to the Court of Appeal amid claims it was too lenient.

The Attorney General's office stepped in to investigate this morning after Aylesford former teacher Stuart Kerner was handed a suspended 18-month sentence yesterday for an affair with a 16-year-old pupil when the judge said she had "groomed" him.

Kerner was convicted of having the sexual relationship, but avoided jail.

Judge Joanna Greenberg QC told him: "Her friends described her, accurately in my view, as stalking you.

"If grooming is the right word to use, it was she who groomed you, (and) you gave in to temptation.’’

This morning the Attorney General's office (AGO) said it would investigate after receiving complaints that the sentence was unduly lenient.

But the office has since tweeted: "We considered whether Stuart Kerner's sentence could be referred to the court of appeal as part of the unduly lenient sentence scheme.

"However Mr Kerner's crimes are not included in this scheme, meaning the law officers are unable to refer this. It's important the public can challenge what they believe to be exceptionally low sentences."

The 44-year-old, of Russett Close, Aylesford, was found guilty of the offences at Inner London Crown Court in December.

The former vice-principal returned there for sentencing yesterday, and was handed the suspended 18-month jail-term.

The jury heard how he had had sex with the girl at Bexleyheath Academy where he worked, and at his Kent home, when she was 16.

Kerner was convicted of two counts of sexual activity with a child by a person in a position of trust.

He was cleared of four counts of the same offence, and also acquitted of two counts of sexual activity with a child.

Judge Joanna Greenberg QC said she believed the victim was "intelligent and manipulative" and "showed no compunction" about lying when it suited her, but that she was also a vulnerable young girl and he had been in a position of trust.

"The law demands that you are the responsible adult and that you show restraint, and we know that you failed to do so," she said.

The case was featured on the front page of the Daily Mail today and has provoked a furore online, with its story attracting 990 comments, mostly critical of the sentence and judge's comments.

“The law is clear that a child under the age of 18 cannot consent to a sexual relationship with a teacher because of the power imbalance. All teachers know this" - Louise Pennington

One wrote: "I have read this report with disbelief, he is a 44-year-old man and a teacher, he broke the main rule of not engaging in sexual activity with a pupil. I do not believe in this 'He couldn't help himself' cobblers, he has an obligation to not get involved."

Louise Pennington of the campaign group Everyday Victim Blaming told the Guardian: “We are deeply concerned by the statements made by Judge Greenberg in sentencing Stuart Kerner for sexually abusing his 16-year-old student.

“The law is clear that a child under the age of 18 cannot consent to a sexual relationship with a teacher because of the power imbalance. All teachers know this.

"Yet Judge Greenberg has accused the child of ‘grooming’ her teacher and has mitigated Kerner’s responsibility because he was ‘emotionally fragile’ about his wife’s miscarriage.

“As is clear from Annex C pf tje guidelines on prosecuting child sexual abuse, a 16-year-old girl cannot ‘groom’ an adult.

“We will be reporting this case to the attorney general due to the low sentence.”

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