The Attorney-General was today facing calls to appeal against a “pathetically lenient” sentence handed to a window cleaner who raped a ten-year-old girl.

Mike Penning, a Conservative backbench MP, said the Attorney-General should call in the court papers after Keith Fenn, 24, was given concurrent two-year and 18-month jail sentences at Oxford Crown Court by Judge Julian Hall for two attacks on the girl in a park.

Fenn could be free within a few months because of the amount of time he has already spent in prison awaiting sentence.

Mr Penning, MP for Hemel Hempstead, said: “This sends out all the wrong signals to paedophiles. This young lady is in care and doesn’t have parents who can stand up for her, so what better job could an MP do?”

In his letter, Mr Penning says: “As I am sure you are aware, last week Judge Julian Hall QC sentenced Keith Fenn to what has been described as a pathetically lenient sentence for the rape of a ten-year-old child.

“Fenn will serve only four months, when the judge could have used his powers to give a much more severe sentence.

“I am appalled at the leniency of this sentence; frankly a sentence this lenient for such a serious crime makes a mockery of the legal system and I call on you to use your powers and appeal against this indulgent ruling.

“What sort of deterrent is this to those who wish physically to abuse our children?

“This child is in care and thus has no parents to support her who can call on you to call in the court papers from the CPS and so, do all you can to get justice for this little girl.”

The case comes after the Attorney-General, Lord Goldsmith of Allerton, released figures last week showing that more than 100 criminals, including murderers and sex offenders, had their sentences increased last year because judges had been “unduly lenient”.

The number was 40 more than in 2005 and will re-ignite the row over “soft judges”.

The outgoing Attorney-General, who will step down tomorrow, also included a roll-call of judges who issued what turned out to be light sentences.

Lord Goldsmith took 143 offenders to the Court of Appeal under his powers to challenge sentences thought to be too lenient.

In 113 cases, the sentence was judged to be unduly lenient and in 108 cases it was increased. This number was the highest in the last six years.

Sentences were increased in seven murder cases, seven manslaughters, 24 cases involving sex abuse, 20 robberies, seven firearms crimes, 18 drugs offences and six deaths by dangerous driving.

Judges dealing with sexual offenders were most likely to let offenders off too lightly, the figures revealed.

For example, Judge Michael Addison, at Guildford, passed a suspended sentence of nine months on a swimming instructor who sexually touched two eight-year-old girls on two occasions. The Court of Appeal increased this to six months’ immediate imprisonment followed by 18 months on supervision. The same judge gave another offender nine months for a sexual assault; this was put up to three years.

The power to challenge a judge’s sentence was introduced by the last Tory Government in the 1988 Criminal Justice Act.

Sir Igor Judge, Head of Criminal Justice and one of the country’s leading judges, defended the courts against the charge of being too soft. He said the statistics showed the system of referrals was “working as intended”.

He added: “Only around 100 cases were referred in the last year and they did not all lead to an increased sentence. To provide some context, there are around 80,000 cases dealt with in the Crown Court in any one year.”

He said judges often worked within highly prescriptive guidelines and a confusing welter of legislation.

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