PARIS (Reuters) - The daughter of L'Oreal heiress Liliane Bettencourt has been placed under investigation for allegedly giving money to an accountant whose testimony in another case helped her protect her mother's fortune, the daughter's lawyers said on Thursday.

Francoise Meyers-Bettencourt was handed control of her mother's finances by a French court in 2011 on the grounds Liliane Bettencourt was suffering from dementia and had been exploited.

The so-called Bettencourt affair initially centred on Francois-Marie Banier, a celebrity photographer whom Meyers-Bettencourt accused of swindling her mother of up to a billion euros.

After the 2011 ruling, however, Meyers-Bettencourt reached a deal with Banier to drop her criminal complaint against him, but prosecutors proceeded with charges.

He was later found guilty and now accuses Meyers-Bettencourt of bribing witnesses to give evidence against him. Her lawyers reject Banier's allegations.

"She lent money with interest and it will be repaid, so it's not a payment," Jean Veil told reporters.

The allegations carry a maximum penalty of three years in jail and a 45,000 euro fine if the case goes to trial and she is convicted.

Banier alleges that Claire Thibout, a former accountant to Bettencourt, received a loan in 300,000 euros in late 2012 and a gift of 400,000 euros for her false testimonies.

Meyers-Bettencourt's lawyers say the loan was made to Thibout after Meyers-Bettencourt had dropped her complaint against Banier and that she therefore had no cause to bribe witnesses against him.

"The case was already closed at this point. It's absurd to think she could have bought off witnesses," said Veil.

Banier was convicted of exploiting Bettencourt in 2015 and sentenced to three years in jail, fined 350,000 euros and ordered to pay 158 million euros in damages. He appealed and faced a re-trial in May. The court will rule on Aug. 24.

(Reporting by Simon Carraud; writing by Richard Lough; Editing by Toby Chopra)