* Book says father told teacher to stay away from son

* Trogneux, 24 years his senior, became Macron's wife

* Macron frontrunner in two-stage presidential vote

By Richard Balmforth

PARIS, April 12 (Reuters) - French would-be president Emmanuel Macron defied orders from his parents to end a schoolboy romance with a teacher who was 24 years his senior - the woman he married and who will become first lady if he is elected next month, a new book says.

When Macron was a young teenager, his father told Brigitte Trogneux, a married mother of three, to stay away from his son until he reached 18 years of age, according to the book.

"I cannot promise you anything," a tearful Trogneux replied. The relationship continued and the couple married in 2007 after Trogneux divorced her husband.

Macron's relationship with Trogneux has inspired intensive coverage by glossy magazines. The publication of "Emmanuel Macron: a perfect young man" adds to the picture in the last weeks of a tight presidential race in which he is a favourite.

The latest publication seemed unlikely to have much, if any, impact on the 39-year-old's election chances.

But the detail of Macron's romance, which began at a Jesuit college in the provinces where he was a teenage schoolboy and Trogneux a teacher, is sure to capture the public imagination in the final days before an election where one vote takes place on April 23, with the run-off on May 7.

He was about 16 at the time and she was in her late 30s. The romance blossomed when he studied drama with Trogneux, the book said.

Journalist Anne Fulda, who interviewed Macron, his wife and both of his parents for the book, said they had been shocked to discover their teenage son, rather than pursuing her daughter, was pursuing Trogneux herself.

"We couldn't believe it. What is clear is that when Emmanuel met Brigitte we couldn't just say: 'That's great!'," Macron's mother was quoted as saying.

She later confronted Trogneux saying: "Don't you see. You've had your life. But he won't have children with you."

"OUR SECRET"

A spokesman for Macron, asked to comment, said it was regrettable that Fulda had not sought Macron and his wife's opinion on his parents' opposition to the romance.

The book left unclear when exactly the romance turned into a full-blown love affair. Fulda wrote: "Emmanuel's parents were keen on emphasising that they did not lodge a complaint against Brigitte Auziere (Trogneux's married name) for corruption of a minor."

And Trogneux, who will become France's first lady if Macron wins the election, remained discreet about the origins of the affair. "Nobody will ever know at what moment our story became a love story. That belongs to us. That is our secret," she was quoted as saying.

The affair continued between the two after Macron left the town of Amiens to continue higher studies in Paris and his subsequent move into banking where he made a fortune before entering politics.

The book quoted him as decrying the "misogyny" generated by his marriage to Trogneux. "Nobody would call it unusual if the age difference was reversed," he said. "People find it difficult to accept something that is sincere and unique.

Fulda said Macron's parents rapidly came round to accepting the relationship despite the early opposition to the romance, quoting Maron's mother as describing Trogneux as "adorable".

The book also recounted how Macron's mother reacted when she heard rumours that her son might be gay, speculation that he himself dismissed at a rally last February.

"You're going to deny this, aren't you!" she said to him. To which he replied: "Of course not, Mum. To reply would only mean feeding unfounded and uninteresting rumours."

(Writing by Richard Balmforth; Editing by Brian Love and Alison Williams)