References check

Hi guys I currently work in the private sector and always wanted to move to the public sector but before I submit an application there is a declaration that I must accept which basically says that they can check all my background including my current employer. Does that mean they would contact my employer before I’m the last candidate they chose or would they contact them while they are still considering other applicants. Because honestly that would put me any a very undesirable situation if they contact the employer and then decide to go with other candidates.