If you've been working on a contract basis for a government department for many years, with annual renewals often involving short breaks, your employer may not be able to simply replace you with another contractual employee without a valid reason. While contractual roles generally don't guarantee permanent positions, courts have ruled against arbitrary replacements and the use of artificial breaks to circumvent employee rights. It's advisable to consult a legal professional specialising in service matters to review your specific situation and explore potential legal challenges.