The ex-bureaucrat, dismissed in 2013 for tweets critical of the federal government, said she was upset and disappointed the court had decided against her.

Ms Banerji outside the High Court said the result on Wednesday, following a six-year court battle, was a loss for all public servants.

"The only advantage of taking this action was to affirm the role of freedom of speech for public servants. And we've failed," she said.

Speaking later at her Canberra home, Ms Banerji said public servants should be able to participate in political discussion.

"I feel very, very sorry, not for me because all my losses had already been incurred," she said.

"But I'm very sorry that the court has cast this terrible shadow over our people.

"There's nowhere to go after this, there's nowhere to go."

Ms Banerji said the only positive part of the result was that it would become a "springboard" for further debate about restrictions on free speech for public servants.

"What I would really like to say is to all the law students that are currently enrolled around the country, please take up the banner and take this further, because this is not a good decision for society and it's not a good decision for our democracy," she said.

"The public servants themselves are good people to make comment about government and democracy because they are actually there at the coal face, and they see it happen day by day."

Ms Banerji's lawyer Allan Anforth, in early comments on the result, said the High Court had taken the view her legal team feared it would.

"It's that public servants, when they take their employment, are giving up rights that other citizens have because of the nature of the public service," he said.

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Mr Anforth said his team's case was that the protection for free speech implied in the constitution extended to everyone.

"What this decision is saying is that public servants are excised from that protection."

The decision reflected an outdated view of the federal bureaucracy that assumed it was a career-permanent profession, Mr Anforth said. Despite this view, the public service had large and changing ranks of contractors.

"This is a really naive decision in terms of the political realities that exist in the community," he said.

The High Court's finding would also reach into the private sector and allow its employers to limit the free speech of workers, Mr Anforth said.

"If the employee is critical of the employer's position on some politically relevant, social issue, they can be sacked," he said.