BRITAIN’S nuclear deterrent is protected from the cyber attacks, which have wreaked havoc across the NHS in Scotland and England, Sir Michael Fallon, the Defence Secretary, has insisted.

Sir Michael ruled out concerns over the threat of viruses on Trident operating systems following the global attack which hit 48 NHS trusts in England and 13 Scottish health boards.

The UK Government had set aside more than £1.9 billion to tackle cyber threats, of which some £50 million went to the NHS, after an official security review highlighted hacks as a major threat, he said.

"We never comment on the different systems, obviously for reasons of security, that our submarines use but our vanguard submarines I can absolutely assure you, are safe and operate in isolation when they are out on patrol, and I have complete confidence in our nuclear deterrent," he told the BBC’S Marr Show.

Pressed further, the Scot said: "I can assure you that the nuclear deterrent is fully protected."

Sir Michael said the NHS had been warned over cyber threats in the months before Friday's attack but every effort was going into protecting the NHS.

He stressed: "Let me just assure you we are spending money on strengthening the cyber defence of our hospital system."

Meantime, the Secretary of State defended the Government's record on military recruitment as army numbers sat at 79,000, below the Government's pledge of keeping the numbers at 82,000.

He said: "First of all, we cannot force people to join the Army, we don't have conscription in this country, the army has to compete with other sectors in the economy.

"It was a promise over the parliament, over the five years, we are only two years into the old parliament and I can assure you that we are spending a lot of money on recruiting but also on giving the armed forces the equipment they need."

Asked about defence spending, he rejected criticism of "accounting deceit", saying the UK's two per cent spend was in line with Nato's target.

Sir Michael hinted at cuts to funding for military equipment despite promises of "the biggest equipment programme in generations" over the next decade.

He said: "That is a ten-year programme and part of the cost of that programme has to come from efficiency savings, getting rid for example of land and barracks and buildings that we don't need, being more efficient in the way that we work."