Tasmanian senator Jacqui Lambie has unleashed on world tennis No.1 Novak Djokovic, as a row escalates about his potential involvement in next month’s Australian Open.

The Serbian is officially listed to play in the year’s first grand slam in Melbourne, but has repeatedly refused to confirm if he is vaccinated against COVID.

The Victorian government is adamant that only fully vaccinated players, their entourages, staff and fans will be granted entry to Melbourne Park.

On Thursday, amid speculation Djokovic might use a loophole to gain a medical exemption for the tournament, Senator Lambie weighed in.

“I don’t know where the loophole comes from. You’re either double-vaxxed or not,” Ms Lambie told Nine’s Today show.

“If you’re not double-vaxxed, like many Australians, I don’t give a stuff whether you’re No.1 or not.”

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Tennis Australia has distanced itself from the controversy, saying exemptions are determined by an independent medical panel determines – and all applications are anonymous.

“There’s an independent panel of medical specialists and they see a blind copy of the medical exemption request,” Tennis Australia and Open boss Craig Tiley told ABC News on Thursday.

“It’s very specific as to what is eligible or not, and then that goes through that expert panel and they will make a call.

Tiley said the Australian Technical Advisory Group on Immunisation guidelines had clear guidelines for an exemption that he considered “different hurdles to cross”.

He said he wasn’t privy to any medical condition that Djokovic might have that would meet the criteria.

“There’s no loophole … international tennis players have exactly the same conditions as everyone coming into Victoria or coming to Australia,” Tiley said.

“There’s no benefit provided to any one of them on any condition and in any circumstance and that’s been made clear to them from the beginning.

“We now are in a position where over six weeks ago only 50 per cent of the tennis playing group globally were vaccinated and now it’s more than 95 per cent.”

Tiley also said the Australian Open entry list released on Wednesday wasn’t final.

“What was published is a general entry list and as a matter of course, everyone goes on the entry list,” he said.

“It’s not a commitment list of about who’s exactly in the draw, that comes in several weeks time.”

The list did confirm that another big name will be absent from Melbourne. Seven-time Australian Open women’s champ Serena Williams has opted out, following advice from her medical team.

“While this is never an easy decision to make, I am not where I need to be physically to compete,” Williams said.

“Melbourne is one of my favourite cities to visit and I look forward to playing at the AO every year.

“I will miss seeing the fans, but am excited to return and compete at my highest level.”

The 2019 US Open champion Bianca Andreescu, 21, has also withdrawn.

-with AAP