He was elected Member of Parliament (MP) for Lifford, County Donegal in 1729 until his death in April 1761, at the age of 61.
Their children were: Up to 1729 his first cousin Colonel Alexander Montgomery shared the parliamentary patronage of Lifford, County Donegal with the Creighton family, the Earls of Erne.
There is an agreement in the Erne papers (held in the Northern Ireland Public Records Office) dated 1727 between Alexander Montgomery and General David Creighton about the sharing of Lifford Corporation and its representation in the Irish House of Commons, to which it sent two MPs.
General David Creighton died in 1728 so the Lifford seat was filled by Thomas Montgomery, the nephew of Alexander.
On the death of Thomas Montgomery in 1761, full control of the Lifford seats passed to Abraham Creighton.