If a person is given a contract of a company to act as the consultant, do they have the right to discipline employees of that company?

generally, no. unless the contract specifically authorizes that, it is the responsibility of company management to discipline own employees.

even if consultant has been given vast powers, it is bad practice. should consultant have that power, and management refuses to discipline employees, the better practice is for consultant to fire the manager(s) in question and replace them. [This is not too uncommon in bankruptcy situations, for example, where the trustee has vast but temporary power.]

NO. A consultant only makes recommendations or does a job independently. The consultant isn't part of the employment chain, so there are no employees for the consultant to discipline.

Not usually. A consultant is a privately contracted individual hired to perform a specific job and usually is not in a position to superviser other employees.

Technically, a "consultant" is NOT an employee of the company and does not have the authority to supervise company employees. HOWEVER, in actual practice, it's up to company management.

No, but they can advise the company to do so.

He has whatever rights the contract gives hiim.

Consultants are not normally attributed the powers of a line manager of the company that has engaged them

That would depend on what the consultant was hired to do. If the company authorizes it, the answer is yes.