The father of an Australian scientist known as 'the human swan' who could lose her legs after a horror paramotor accident in Britain has just 24 hours to prove he's her dad before his travel exemption is refused.

Sacha Dench, 43, was trying to circumnavigate Britain in a motorised steel parachute with Dan Burton, https://www.femgeeks.net/ 54, when she plummeted from the sky after colliding with a member of her support crew on September 19.

Mr Burton died at the scene and Ms Dench was rushed to hospital in Aberdeen, northeast Scotland, with critical injuries.

Her father Steve Dench, who lives in Queensland, said on Sunday morning that the Australian Department of Home Affairs demanded to see her birth certificate to verify their relationship - which he does not have.

Australians are banned from leaving the country unless they plan to stay overseas long term or get a compassionate exemption.

Citizens leaving on compassionate grounds must prove travel is absolutely necessary with letters from doctors and relationship documentation - like birth or marriage certificates.

'Home Affairs have asked for a copy of her birth certificate or documentary evidence of our relationship.

I do not have this,' he wrote in a Facebook group.

'I was only notified at 11.26pm on Saturday night and have until midnight tonight to provide this.'

Mr Dench explained that he applied for a new birth certificate through Births, Deaths and Marriages, but the document may not arrive for weeks.

He also said the department would not speak with him on the phone until unless his exemption has been refused.