Public servants have a ''special job'' and should be unsurprised if they are disciplined - even sacked - for criticising the government, an employment law specialist says.

Last week, the Federal Circuit Court rejected Michaela Banerji's application to prevent the Immigration Department from sacking her, after she had used an anonymous Twitter account to criticise Australia's refugee policies.

Michaela Banerji was sacked last year from her job after she criticised her department via an anonymous Twitter account. Credit:Jay Cronan

Ms Banerji had argued that any finding of misconduct against a public servant ''for expressing a political opinion contravenes the implied constitutional freedom of political communication''.

However, Judge Warwick Neville said past High Court cases showed that Australians' implied rights of political expression were limited and did not ''provide a licence … to breach a contract of employment''.