Gavin Williamson faced outrage from Labour, the Liberal Democrats and the legal establishment for telling the Mail that Britons who had fought in Syria and Iraq were legitimate targets for military strikes

The Defence Secretary stood his ground last night in the face of a furious row over his suggestion British terrorists should be killed.

Gavin Williamson faced outrage from Labour and the legal establishment for saying Britons who fought for Islamic State in Syria and Iraq were legitimate targets for military strikes. He said the UK should do everything it could to ‘eliminate that threat’.

Mr Williamson was accused of being ‘juvenile’ and of endorsing illegal action more suited to a ‘Netflix series’ after saying: ‘A dead terrorist can’t cause any harm to Britain.’

But he refused to back away from his remarks and said he believed he had the backing of the public.

‘The British people want to make sure that our streets are safe,’ the Defence Secretary said. ‘The British people are incredibly proud of our Armed Forces, the work they do – making sure that the people who are a threat to this country are not able to continue to threaten this country.

‘That’s what the British people want to know that their Government is doing. That is what we will continue to do.’

Former military chiefs also supported Mr Williamson. Colonel Richard Kemp, who commanded UK forces in Afghanistan, said: ‘We are fighting a war against these people. You don’t fight a war by constantly taking prisoners, you fight a war by killing your enemy.’

‘The British people want to make sure that our streets are safe’, the Defence Secretary said, when questioned about the row onboard HMS Queen Elizabeth (pictured)

He added: ‘If you are dealing with terrorists who return from Syria and Iraq and try to prosecute them, it is very hard to get sufficient evidence to do so.

‘That’s a real danger, because it ends up with these returnees back on the street.’

The scale of the threat was graphically illustrated by new figures yesterday, showing that terror arrests had soared to a record high. A total of 400 suspected extremists were held in counter-terror swoops in the year to September.

At the same time, experts said MI5 had the resources to fully monitor only one in every 50 of the 3,000 jihadis who spy chiefs consider worthy of active investigation.

Yesterday, a friend of the Manchester bomber Salman Abedi was convicted of terrorism charges for travelling to Syria to join Islamic State. Mohammed Abdallah - who was linked to Manchester Arena bomber Salman Abedi (right) - has been convicted of being a member of ISIS

Mr Williamson’s remarks to the Mail sparked a fierce backlash yesterday, with the Defence Secretary accused of appearing to ‘endorse a clear breach of humanitarian law’.

HAMMOND PAYS CASH HE OWES THE MoD Philip Hammond has paid the money he owed to the Ministry of Defence for flying on RAF jets and is no longer banned from using them, it was claimed yesterday. Mr Williamson told the Mail on Wednesday that ministers who did not pay for use of RAF jets ‘don’t get to use them’, escalating a row with the Chancellor. But yesterday it emerged the Treasury had finally paid the bill. Advertisement

Lord Macdonald, the former Director of Public Prosecutions, said suggesting dead terrorists could not cause any harm to Britain was a ‘juvenile response’.

He told the BBC: ‘We can’t simply say that everyone who has gone to Iraq will be hunted down and killed. That’s a juvenile response.

'A policy which says we will simply kill every individual who has travelled to Syria or to Iraq, even if they are surrendering, even if they have laid down their weapons, is really a policy that belongs in a Netflix series more seriously than it belongs in the range of policies that should be being applied by the UK Government.’

Liberal Democrat defence spokesman Lord Campbell said Mr Williamson’s comments were ‘ill-considered and appear to endorse a clear breach of humanitarian law’.

Labour MP and former paratrooper Dan Jarvis said his comments were ‘morally, legally and practically wrong’.

Lord MacDonald, pictured in the House of Lords last month, branded Gavin Williamson's remarks 'juvenile'

Labour MP and former paratrooper Dan Jarvis said his comments were 'morally, legally and practically wrong'

Even Cabinet colleague Boris Johnson appeared to distance himself from the comments, saying: ‘I think that ... Michael Fallon put it very well a few weeks ago when he said that anybody who goes to fight for Daesh in Syria or Iraq has got to understand that they are putting themselves in harm’s way and, indeed, making themselves legitimate targets of British Armed Forces, and that is the reality.’

Meanwhile, Britain’s terror watchdog Max Hill – who had said that some British jihadi fighters should be allowed home to re-join society – hit back by insisting that criminal prosecution was ‘inevitable’ in most cases where UK citizens returned.

He tweeted: ‘Criminal prosecution (is) inevitable in most cases where UK citizens return, and where evidence of committing serious criminal offences.’ This is despite the fact just eight of the estimated 400 British foreign fighters who have travelled to Syria and Iraq and since returned home have been convicted of an offence.

Theresa May’s official spokesman said: ‘The Government position on this has been made clear a number of times in recent months, which is that if you travel to Iraq and Syria and if you are fighting with our enemies there, then you make yourself a legitimate target.’

3,000 suspects, but just 60 watched full-time

MI5 can monitor only one in 50 of the 3,000 jihadis considered worthy of investigation, it was revealed last night.

Restricted resources mean the security services can monitor only 60 terrorist suspects around the clock. A surveillance operation requires 30 officers per suspect, plus manpower to monitor electronic communications.

It came as the Home Office revealed the number of terror arrests in Britain has surged to a record high after a wave of deadly attacks.

Some 400 suspected extremists were held in counter-terror swoops in the year to September. The rise of 54 per cent from 259 in the previous year came as the UK threat from jihadis and far-Right extremists reaches unseen levels. There were five lethal terror attacks in the UK between March and September, killing 36, for which a total of 64 suspects were detained.

Earlier this week, Home Secretary Amber Rudd disclosed that Britain’s police and spies had foiled nine plots since the Westminster Bridge attack in March – and thwarted 22 since the murder of soldier Lee Rigby in May 2013.

But restricted resources mean only a fraction of the hundreds of suspected Islamist extremists at large can be subject to intensive full-time surveillance at any one time. The Home Office data revealed that 12 suspects were held after the attack at Westminster Bridge, 23 in connection with the bombing at Manchester Arena, 21 over the London Bridge atrocity, one arrested after the Finsbury Park mosque attack and seven linked to the Parsons Green Tube blast.

Some 58 of the 400 arrests were of suspected female extremists, the highest since records began in 2001. Eighteen were under 18, more than any other year. The number of white terror suspects held is at a new high of 143.

The statistics also show that the number of people in prison for terrorism-related offences reached 213 – an increase of 44 on the previous year.