Elle Macpherson is reportedly planning to have another child.

The 51-year-old supermodel - who already has sons Flynn, 17, and Cy, 12, with ex-partner ARPAD BUSSON - and 45-year-old husband Jeffrey Soffer are keen to have a baby together and are said to have decided to use a surrogate to expand their family after the Australian beauty failed to conceive naturally.

A source said: ''They realised after a few months that having a baby naturally was a lost cause and they barely discussed adoption - they agreed on surrogacy quite quickly.

''Elle is thanking her lucky stars she had the foresight to freeze her eggs years ago. She figured they'd come in handy.''

Following a number of consultations with fertility experts, the couple - who married in 2013 - have now found a surrogate, but are keeping her identity under wraps.

The source added to Australia's Woman's Day magazine: ''They're keeping the identity of the surrogate a secret. It's what she wants and it's what they want. But I do know she's in her 30s and has two children of her own.''

Elle and Jeffrey - who has three children from a previous relationship - began dating in 2009 but split in April 2012.

They reconciled in November of that year, after the hotel heir was involved in a helicopter accident.