Dictionary of English - collective noun

When such a group is considered as a single unit, its collective noun is used with a singular verb and singular pronouns: The committee has reached its decision. But when the focus is on the individual members of the group, British English tends to use a plural verb and plural pronouns with its collective nouns: The committee have been arguing all morning over what they should do. American English usually uses a singular verb and pronouns in these circumstances.

A determiner in front of a singular collective noun is always singular: this committee, never these committee (but of course when the collective noun is pluralized, it takes a plural determiner: these committees).