A US visa category could potentially be a model to allow thousands of skilled Australians to work in the United Kingdom post-Brexit, according to Foreign Minister Julie Bishop.

The Federal Government has repeatedly made it clear it is "enthusiastic" about discussing better visa arrangements for Australians, alongside any free trade negotiations with the UK.

On a visit to London, Ms Bishop said the reciprocal USA E-3 visa for skilled workers is an example of how freer movement might be achieved.

It was negotiated between Australia and the United States in 2005 at the same time the countries were finalising a trade deal.

"I hope that when we commence negotiations for a free trade agreement [with the UK]… that we will be able to have this discussion as we did with the United States," Ms Bishop told reporters.

"We have a precedent, we have a model, an option that we can use in our discussions."

The E-3 visa is only available to Australian nationals, their spouses and children and is reserved for people working in a specialty occupation in the United States.

More than 10,000 are offered each year, though that cap has never come close to being reached.

The United Kingdom has always been a popular destination for young Australians — roughly 12,000 took advantage of the two-year Youth Mobility Scheme in 2016.

But after the age of 31, getting a visa becomes more difficult and, unless an applicant has a British ancestor, can often require sponsorship through an employer.

'Positive messages' from UK

Julie Bishop said the UK is open to discussions about greater visa access. ( ABC News: Jed Cooper )

The Foreign Minister said there have been "some very positive messages" from the British side about greater visa access.

The most vocal proponent of the idea in the UK Cabinet is Foreign Secretary Boris Johnson, who said he campaigned for Britain to leave the EU, in part to "reinvigorate ties" with the Commonwealth.

But when he floated the visa idea publicly in 2016, Mr Johnson was slapped down by Home Secretary Amber Rudd, who campaigned against Brexit.

She said there were "no plans" to increase immigration from Australia.

In response to the ABC's questions about its post-Brexit plans, the British Home Office said it was "considering a range of options for the future immigration system" to ensure it is managing immigration at a "sustainable level in the national interest".

Australia and the UK will only be able to negotiate a free trade deal if Britain leaves the European Customs Union when it exits the European Union.

The British Government has said it will leave, but membership of the customs union is a hot topic of political debate in the country at the moment.

Ms Bishop said she would not tell her UK counterparts what they should do but said Australia's "national interest" would be served if the country does leave.

Bishop to raise Poland's controversial legal changes

The Foreign Minister is also visiting Slovenia and Hungary on her current trip.

She said she will have the opportunity to raise Poland's highly controversial overhaul of its court system when she meets officials from the country at a gathering in Budapest.

The EU fears the judicial changes put the rule of law in Poland at risk and has started an unprecedented process that could eventually see the nation face sanctions.