The Army will shrink its staffing target by around 10,000 troops by 2025 in a major overhaul of the military aimed at boosting drones and cyber capability.
Defence Secretary Ben Wallace argued technological advances mean “greater effect can be delivered by fewer people” as he broke a Conservative pledge in the last election to maintain the size of the military.
With troop numbers dropping to the lowest level since 1714, Mr Wallace urged MPs not to play “Top Trumps” with force numbers as he detailed a a major modernisation of the armed forces on Monday.
But Defence Committee chairman Tobias Ellwood warned against the “dramatic cuts” to conventional military strength as Labour criticised the plan “for fewer troops, fewer ships, fewer planes”.
The changes set out in a defence command paper include £3 billion for new vehicles, long range rocket systems, drones, electronic warfare and cyber capabilities.
Numerous aging RAF planes will be retired, as will the oldest Chinook helicopters, while Navy frigates and destroyers drop from 19 to 17 in the coming years.
A third of the 227 Challenger tanks will be scrapped, with the rest of the fleet being upgraded at a cost of £1.3 billion.
Mr Wallace argued that the Army has not been at its “established strength” of 82,000 since the middle of last decade, but that it would reduce from 76,500 “trade trained personnel” currently to 72,500 by 2025.
“The Army’s increased deployability and technological advantage will mean that greater effect can be delivered by fewer people,” he 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.”
Following the publication last week of the Integrated Review of foreign and defence policy, Mr Wallace argued that previous reviews were “overambitious and underfunded, leaving forces that were overstretched and underequipped”.
But, anticipating the anger from some Tory MPs, he recalled his own Army experience that despite the troop numbers boasted “it was in truth a hollow force”.
Mr Ellwood, a senior Conservative backbencher, welcomed investment in cyber as among the advances but warned “they come at a huge price to our conventional defence posture”.
He said there are “dramatic cuts” to troop numbers, tanks and RAF aircraft, which he suggested would not pass if the plans were put to a Commons vote.
For Labour, shadow defence secretary John Healey warned his counterpart in Government that “size matters”, adding: “This is a plan for fewer troops, fewer ships, fewer planes, over the next few years.”
The cuts come despite the Prime Minister definitively ruling out any when launching his manifesto for the 2019 general election.
“We will not be cutting our armed services in any form. We will be maintaining the size of our armed services,” he said.
The Government argued modernisations are needed to create a more agile military able to counter evolving threats around the globe in a defence command paper published on Monday.
Titled “Defence in a Competitive Age”, it sets out how forces will spend more time deployed overseas to support allies and deter hostile powers such as Russia, which was identified in the Integrated Review as the “most acute threat” to the UK.
More than £2 billion will be invested over the next four years in the Future Combat Air System, while £1.5 billion will be spent to create a “digital backbone” to share data.
Mr Johnson spoke to Nato secretary general Jens Stoltenberg ahead of the Government detailing the major overhaul.
The Prime Minister told him of the “wholescale modernisation” of the armed forces and said a £24 billion increase in the defence budget brought spending to “significantly above the Nato target”, according to No 10.