LONDON – British scandalmongers are still dishing the dirt about Diana.

Socialite Lady Colin Campbell claims in a new book that the tragic princess had a secret abortion after an affair with a wealthy art dealer. The shocking allegation in “The Real Diana” comes as NBC airs tonight on “Dateline” a private tape Diana recorded in which she pours out her heart about her broken marriage.

Campbell claims Diana became pregnant in 1994, when she was separated from Prince Charles – but not yet divorced.

The book does not name the supposed baby’s father, but in 1994 Diana was known to be in love with art dealer Oliver Hoare, a married pal of Charles.

That summer, she made dozens of nuisance calls to his home, which his wife reported to police. Scotland Yard traced them to Diana’s private phone line at Kensington Palace and to phone booths near the palace.

According to the book, which relies heavily on anonymous sources, Diana was pregnant when she made the obsessive phone calls. “How could she have a baby? She wasn’t divorced. She couldn’t have an illegitimate baby. She couldn’t do that to William and Harry,” an unnamed earl’s daughter says in the book.

She claims Diana “freaked out” and wanted the baby, saying, “Suppose it’s a girl.”

Campbell, who has a scandalous history of her own, has written several books about the royals. Born in Jamaica with deformed sexual organs, she was brought up as a boy but had corrective surgery at 21 and married Lord Colin Campbell, the second son of the Duke of Argyll. Their brief marriage ended in an acrimonious divorce.

The book contends that Diana used an appointment with her financial adviser, Joseph Sanders, who died last year, as a coverup for the alleged abortion.

Sanders’ ex-wife Anita told the Mail on Sunday that she knew about the abortion at the time.