In short – yes!
If a casual has been employed on a ‘regular and systematic basis’ for 6 months (or 12 months if the employer has fewer than 15 employees), then they will be entitled to bring an unfair dismissal claim if they are sacked.
An employee is likely to be considered to have been employed on a ‘regular and systematic basis’ if they are engaged frequently over the relevant period of time, even if the working hours and times vary.
Although each situation will be considered on its own merits, employers should take note that employing a casual workforce provides no magic shield against the risk of unfair dismissal claims.