The Defence Command Paper published last month confirmed the Army is to be cut to 72,500 by 2025 - 4,000 less than the current 76,500 soldiers.
The Shadow Armed Forces Minister was speaking at the despatch box before MPs are due to vote on the plan.
Mr Morgan said: ‘The defence of the realm is the first priority of any government, but this one is playing fast and loose with our country’s strategic security plans and its commitments on defence spending.
Woman, 44, whose large Dobermann dog mauled girl, 3, on Leigh Park street released back into neighbourhood by police
WATCH: This is the moment a man with a grudge fire-bombed a family's garden in Leigh Park
Four people hospitalised after 'serious' multi-vehicle crash involving lorry on A27 near Chichester
Council refuses to close Gosport splash park despite it leaking 'thousands of litres of water'
Community in horror after little girl suffers ‘life changing injuries’ after being attacked by Dobermann dog in Leigh Park
‘Labour is determined to ensure our country can protect itself properly, now and in the future, which is why the official opposition is forcing a vote in Parliament today on this important issue.’
The reduction in personnel follows on from 45,000 troops having been cut since 2010.
Mr Morgan, added: ‘The government’s track record speaks for itself. A decade of decline for personnel numbers and investment in defence; a strategic defence plan that does not clearly match capabilities to current and future threats; broken promises to our Armed Forces.’
Speaking following the publication of the paper, defence secretary Ben Wallace said: ‘These changes will not require redundancies and we wish to build on the work already done on utilising our reserves to make sure the whole force is better integrated and more productive.’