John Brown, 60, is accused of five counts of indecent assault against two girls under the ages of 13 and 16 at different times and locations in the North and in England during the 1970s.
He denies the alleged abuse or that his 62-year-old sister helped him to cover up the allegations.
However, Claire Howell, for the prosecution, told a jury of six men and six women at Harrow Crown Court in north-west London that the pair had both lied during Brown’s three-week trial.
“This defendant says that the complainants are lying, he says that this is a wicked conspiracy involving both women,” Ms Howell said during her closing speech.
“He says that all the witnesses who have given evidence for the prosecution are part of an evil conspiracy to accuse him of abuse that he did not commit.
“The prosecution say that the people who have agreed to lie to you in this case are the defence witnesses.
“It’s no sophisticated conspiracy, it’s a cover-up from many years ago, at a time when you might think that cover-ups of this sort did happen for various reasons.
“And, having covered it up, it’s very difficult for them to come clean about it for various reasons.”
Ms Howell said Mr Brown and his sister had given a “slick presentation” to the court, with exact dates and details.
However, she said what the complainants remembered most was how they felt when they were allegedly abused.
And she claimed that the defendant, from Bracknell in Berkshire, had confessed the abuse to several people, saying of one of the complainants: “She came on to me.”
Ms Howell added: “This family, the defendant and his sister, have known about this for years. They have all known about this for a very, very long time.”
Ms Scallon is facing defamation proceedings here brought by one of the complainants against her brother over a 2011 television interview.
Martyn Bowyer, for the defence, described the prosecution’s case against Mr Brown as “fuzzy” on the details.
He said his client was an innocent man who had been “consistent throughout”.
He asked the jury not to be influenced by recent high-profile child abuse scandals. “Offences of these kind are by their very nature highly charged,” he said.
“Child abuse, wherever it takes place, is abhorrent. At the moment you cannot open a newspaper without being confronted with a new scandal. Whether it is TV personalities, politicians or just ordinary members of the public — it is the prevalent topic of the day. But I beg of you, do not let other cases or other personalities in any way colour your judgment and your verdicts in this case.”