From one review of Ireland and the British Empire (which I’ve just ordered from amazon.co.uk):

Apparently de Valera was furious with Costello when he announced, in 1948, that the newly declared Republic would be leaving the Commonwealth, shortly before India and Pakistan announced that, as republics, they would stay in, on just the sort of terms as de Valera had wanted.

Full book details: Ireland and the British Empire (Oxford History of the British Empire Companion Series), edited by Kevin Kenny (OUP, 2006)