LONDON (Reuters) - Prime Minister David Cameron said on Tuesday that a suspected chemical weapons attack in Syria was "absolutely abhorrent" and necessitated action from the international community with Britain considering a "proportionate response".

A spokesman for Cameron said the prime minister was aware of the need to "make a clear case" if he did take a decision to use force, saying Britain's armed forces were making sure they were in a position to respond militarily if asked to do so.

"It's reasonable to assume our forces are making contingency plans," the spokesman told reporters, stressing that no decision to use force had yet been taken and that any decision to do so would be based on evidence from "a range of sources".

Cameron cut short his holiday to return to London and will announce later on Tuesday whether he will recall parliament, which is in summer recess, to discuss how best to respond to the latest events in Syria. Cameron believed parliament should have its say on such matters, the spokesman said.

Cameron will chair a meeting of the National Security Council on Wednesday to discuss the matter and is expected to keep talking to other world leaders in the meantime to make sure any response is coordinated.

"Any decision taken will be taken under a strict international framework. Any use of chemical weapons is completely and utterly abhorrent and unacceptable ... and the international community needs to respond to that," said the spokesman.

(Reporting by Andrew Osborn; Editing by Stephen Addison)