Duke Eddington wrote:
It's not an abbreviation though, it's a contraction. If it starts and ends with the first and last letters of the word it is replacing, there is no full stop. For example Dr, Mr, Ltd and St, but if it doesn't then there is a full stop. Esq. Prof. Co. etc. A good example to explain this is, Rt Hon. which uses both a contraction and abbreviation.
And there was me saying I didn't want to be pedantic.
True, since abbreviation and contraction have the same outcome, ie they result in a shortened version of the word.
However, whether abbreviation or contraction, traditional grammar requires a dot/point/stop to be placed after. Dr, Mr, Ltd, St all require stops. That is simply called full punctuation, as opposed to the more common open punctuation used today. It's purpose is to indicate something missing, which there is in both the contraction and the abbreviation (because a contraction is an abbreviation).
PS: I wouldn't take anything applied in Parliament as an indication of general usage!