Is 'y' a consonant?

An article in today's Independent about Carol Vorderman's departure from the TV programme Countdown is entitled 'Two consonants and a vowel for Carol: Bye'. But is y a consonant? In words like sky, happy, myth and, indeed, bye, it acts as a vowel. In phonetics, which is the study of the sounds of languages, y is called a semivowel, as it is a sound somewhere between a consonant (where the flow of breath is obstructed or restricted) and a vowel (where the breath travels relatively freely through the vocal tract). The sound w is also a semivowel in English. Another word for semivowel is glide.