The British defence secretary has revealed plans to invest £7m in a swarm squadron of drones theoretically capable of jamming enemy air defences, in a bellicose speech in which he spelled out how the UK could “enhance its lethality” after Brexit.

Gavin Williamson said he wanted the RAF to form a new “concept unit” composed of hundreds of small flying craft, although some experts in the field questioned whether the technology described existed yet.

The UK would “develop swarm squadrons of network-enabled drones capable of confusing and overwhelming enemy air defences”, Williamson said, and he promised to have them “ready to be deployed by the end of this year”.

Information about Williamson’s plans was scant beyond a few remarks contained in a speech intended to present Brexit as an opportunity to “strengthen our global presence, enhance our lethality and increase our mass”.

One expert, Chris Cole, from Drone Wars UK, an NGO that monitors the use of armed drones, said he thought the defence secretary had overblown the idea. The idea of swarm drones was “very much at the concept stage, and it’s very unlikely he can meet the deadline of the end of the year,” he said.

The MoD indicated the exact design had not yet been tendered for, although insiders said the new drone unit would be used to locate radar and missile systems from countries such as Russia and China, and allow British or other aircraft to avoid or destroy them.

Unmanned military drones. Photograph: Northrop Grumman/EPA

Williamson argued that defence would be “pivotal in reinforcing Britain’s role as an outward-looking nation” after Brexit. In a speech designed to bolster his position on the Tory party’s right, he added: “We should be the nation that people turn to when the world needs leadership.”

Williamson announced that the MoD would spend £65m “to improve offensive cyber” – hiring extra hackers who could target foreign networks – in conjunction with GCHQ. He also highlighted plans to buy “pioneering robotic fighting” vehicles, such as self-driving tanks.

Britain has made extensive use of drone strikes in Iraq and Syria since 2014, firing more than 4,100 missiles and bombs in a total of 1,925 strikes, according to information complied by Drone Wars UK, based on official data. But the minister’s proposal would amount to an extension of the concept.

Downing Street played down another of Williamson’s suggestions, that Britain’s new aircraft carrier, HMS Queen Elizabeth, could be sent to the South China Sea as part of its maiden voyage to assert freedom of navigation rights in a region where China has expanded its territorial claims.

Williamson said the passage of Royal Navy vessels through the South China Sea would “give other nations confidence” as well as show Britain was “standing up for our values”, and he said the HMS Queen Elizabeth would travel through the Pacific at some point in 2021.

However, No 10 said precise details of the first deployment of the aircraft carrier in the region would be “agreed by the prime minister in due course” – rather than being decided by the defence secretary alone.

Analysts said Williamson’s attempt to talk up a hi-tech future for the armed forces implied billions in extra spending, and a bid for more money when the comprehensive spending review begins later this year.

Prof Michael Clarke, a fellow at the Royal United Services Institute thinktank, said the armed forces would need an increase in spending from the existing 2.1% of GDP to around 2.5% “just to fill the holes, which would be an extra £8bn or £9bn a year”.

Clarke added: “It would be only if you increased that to 2.7% that the MoD would be able to spend on new things of the type that Williamson is talking about.” Under the Conservatives and the previous coalition government, defence spending has fallen as a proportion of GDP from 2.5% in 2010.

Williamson also said he wanted to permanently deploy a warship with supporting vessels and helicopters “east of Suez in the Indo-Pacific”, as part of a strike group strategy reversing a policy to withdraw British bases from the region that dates back to 1968.

One Labour MP criticised Williamson’s global Britain emphasis and argued that it was the UK’s European relationships that were critical. “You don’t have to know much history to know why Europe is and will remain central to our military posture or that cooperation and peace in Europe is what allows us to invest in global strength,” said Chris Leslie.