A former aide to Prime Minister David Cameron downloaded images of scantily-clad girls as young as 10, but denies the pictures were indecent, a court has heard.

Patrick Rock, 64, admits downloading 20 images of nine girls to his iPad tablet from a free-to-view website over three days in August 2013, and jurors at his trial on Wednesday were told they would have to decide whether the pictures broke the law.

The prosecution argued the images showed girls, although not naked, in "sexual" poses that drew attention to their genital and breast areas.

But Rock's defence lawyer compared the images to Britney Spears' video for her 1998 song ... Baby One More Time, which she made when she was 16.

The jury at Southwark Crown Court was shown the images, which featured identified girls aged 10 to 16 posing in clothing including bikinis, hot pants and a bra, suspenders and a ballet tutu.

Prosecutor Tom Forster said the youngest girl was 10 years and four months old when the pictures were downloaded in 2013, and the oldest 16 years and seven months, meaning they were all younger than that when the photos were originally taken.

He said all were photographed in such a way as to draw attention to their genital areas, despite them being covered by clothing.

He said: "The clothing the children are wearing is sometimes adult in style - indeed what an adult might consider sexualised or erotic clothing.

"The child is photographed in a pose that is deliberately sexual in tone, because they are scantily clad and/or their legs are often apart and/or they are showing their bottoms to the camera."

Rock did not give evidence but his lawyer, Sasha Wass QC, told jurors they would have to decide whether the images were worth "criminalising" a man of previous good character over.

There was no nudity and the most the prosecution could say was they showed "young girls in sexually suggestive poses", she said.

Ms Wass told the jury they did not know why Rock downloaded the images "but we can guess".

She added: "Young girls are attractive. Some are cute and adorable and we live in a society where there is an allure that is youth."

She went on: "Before deciding that a man of 64 with no criminal convictions should be convicted as a criminal, you might want to bring to mind other images of young girls that are freely available.

"Some of you will be old enough to remember the 1998 video of the 16-year-old Britney Spears gyrating in a schoolgirl uniform for Hit Me Baby One More Time. When that was made in 1998, Britney Spears was under the age of 18. She was wearing provocative clothing and her words and movements could not have been more suggestive."

Ms Wass also used the example of Lewis Carroll being "captivated" by young Alice Liddell, the inspiration for his Alice in Wonderland, saying pictures Carroll took of the young Alice aged 10 could be found in books on sale in shops.

She said child protection was an important priority for society, but added: "You may think that there is an element of madness that has been allowed to decide what is decent. Parents are stopped from photographing school plays and people have been investigated for taking pictures of their own children in the bath. You have to ask if that is the society we want to live in."

She added: "In a world where youngsters routinely send selfies of various parts of their bodies to each other, should Patrick Rock be labelled as an outcast for clicking on these 20 images?"

Judge Alistair McCreath told the jury: "The word 'indecent' has no particular legal meaning.

"At one end is the downright obscene and at the other is that which is distasteful. Somewhere in between is that which is indecent. 'Indecent' is against the law, 'bad taste' is not."

Rock, of Fulham, south-west London, denies 20 charges of making an indecent photograph of a child between July 31 and August 31 2013.

The jury retired to consider their verdicts on Tuesday afternoon and will continue their discussions on Wednesday morning.