David Cameron today called on Barack Obama to put pressure on companies like Facebook and Twitter to do more to catch terrorists online.

The British Prime Minister and US President have presented a united front in Washington, unveiling joint cyber-security plans and a commitment to securing long-term economic growth.

But the two countries remain divided over the extent to which social media firms should have to open up their networks to spy agencies on both sides of the Atlantic.

David Cameron held talks in the Oval Office today with Barack Obama, which focussed on plans to step up efforts to prevent cyber attacks

During his US visit, David Cameron today visited tech firm EdClub, as he issued a warning that internet firms must do more to help in the fight against terror

Barack Obama and David Cameron, meeting in Washington last night, are divided over the extent to which social media sites should help in the fight against terrorism

Mr Cameron held talks in the Oval Office today with Mr Obama, which focussed on plans to step up efforts to prevent cyber attacks.

The PM warned cyber-hackers pose a 'real threat' to the City of London and revealed one attack cost a firm over £800million.

He stressed there was 'need for a panic' because Britain was in a very strong position, and working closely with the US.

Ahead of the meeting in the Oval Office, Mr Cameron said: 'Just as we have worked with our closest ally, the US, to protect our people and our countries from traditional threats, so we must work together to defend ourselves from new threats like cyber-attacks.'

However, he was also expected to use the meeting to press for more to be done to make the likes of Facebook do more to stamp out and report terrorists using their networks.

Mr Cameron insists the security agencies must be able to intercept communications between extremists and terror suspects who use encrypted messaging services and social media sites to plot atrocities.

But the White House has been cool on the idea, arguing a 'balance' must be struck between privacy and national security.

A report last year into the murder of Fusilier Lee Rigby in London concluded that Facebook failed to pass on information that could have prevented his death, and that the website is a 'safe haven for terrorists'.

Mr Cameron insists the security agencies must be able to intercept communications between extremists and terror suspects who use encrypted messaging services and social media sites to plot atrocities

The PM and President have agreed an unprecedented level of co-operation on cyber crime

One of his killers, Michael Adebowale, used the site to express his intent to murder a soldier 'in the most graphic and emotive manner' five months before the attack, Parliament's intelligence and security committee found.

Facebook had previously shut down his accounts because he'd discussed terrorism – but failed to relay concerns to the security services.

Speaking ahead of his talks in Washington today, Mr Cameron said he would raise the issue with the President.

He told BBC Radio 4's Today programme: 'Britain and American face the same challenge. We need to be able, in extremis, to interrupt the contacts between terrorists, whether they are using fixed phones, mobile phones, or the internet. We need to work with these big companies.

'We have good relationships with them, to make sure that we can keep people safe.

'So it's a conversation to have with the President, which I've been doing today and tomorrow, but a conversation we both need to have with the companies concerned.'

Michael Adebowale (left) wrote about murdering a soldier online before he killed Lee Rigby (right) in London

Asked what more he wanted US tech firms such as Facebook, Apple and Twitter to do, the Prime Minister told reporters: 'They need to work with us. They need also to demonstrate, which they do, that they have a social responsibility to fight the battle against terrorism.

'We shouldn't allow safe spaces for traits to communicate. That's a huge challenge but that's certainly the right principle.

'Of course people want privacy in their communications. Nobody wants to listen to the phone calls or read the emails of people as they go about their daily lives.'

The US has taken a less strident stance on accessing social media communications in the wake of the revelations about the activities of the National Security Agency, leaked by Edward Snowden.

White House spokesman Josh Earnest said: 'I think our British counterparts would agree that it is imperative that we properly balance the need for government, intelligence agencies and national security agencies to access to certain kinds of information to try to protect their citizens.'

British and American spies to carry out fake hacking attacks on banks, airlines and nuclear plants

David Cameron and Barack Obama make their way from the Oval Office to the Residence to begin their working dinner last night

Britain and the US are to set up a joint 'cyber squad' to carry out fake hacking attacks on banks, aircraft and nuclear power plants.

In talks at the White House today, David Cameron and Barack Obama are set to agree an unprecedented level of co-operation, with a team of agents to help safeguard both countries.

A report from British spy chiefs to be published today says four in every five big firms in the UK last year experienced some sort of serious cyber security breach.

Mr Cameron and Mr Obama dined together in the White House last night, Attackers range from lone criminals to rogue states seeking to steal industrial secrets or spread mayhem and fear.

There is mounting concern that Islamic fundamentalists or an enemy country could seek to mount a crippling attack on Western banks, sensitive sites such as atomic power plants or even planes, by targeting air traffic control systems.

In the wake of North Korea's attack on Sony Pictures, UK and US security services will now establish a joint team of agents to confront the issue and respond to attacks.

Agents at GCHQ and MI5 will work with their US counterparts to encourage information about threats to be shared at a greater pace. They will also conduct a series of 'war games' to test the resilience of both the UK and US in the face of cyber attacks.

The first exercise will simulate an attack on the financial sector, for example on banks in the City and Wall Street, and will take place later this year.

This will be followed by further 'war games' to test critical national infrastructure – likely to include air traffic control, power stations and healthcare systems.

The US and UK have also agreed to align cybersecurity standards to ensure multinational firms receive consistent advice on keeping their systems safe from cyber attack.

The two countries will train up a new generation of 'cyber agents' and allow the brightest experts on both sides of the Atlantic to carry out research placements for up to six months.

Mr Cameron, who began two days of talks at the White House last night, said: 'Just as we have worked with our closest ally, the US, to protect our people and our countries from traditional threats, so we must work together to defend ourselves from new threats like cyber attacks.

'This is an evolving threat which poses a real risk to our businesses and that's why we're taking our cooperation with the US to an unprecedented level.

'This is about pooling our effort so we stay one step ahead of those who seek to attack us.'

The pair appeared to be in good spirits as they chatted before settling down to business

WHAT'S ON THE MENU? PM AND PRESIDENT OPT FOR LAMB The leaders' discussions were undertaken last night during a 'working dinner'. Judging by the menu, it looks to have been one of Mr Cameron's more enjoyable duties. Pickled Wild Mushrooms, Heirloom Tomatoes

Roasted Red Onion Vinaigrette, Vermont Goats Cheese

Herb Crusted Lamb, Preserved Lemon

Roasted Artichokes, Orzo Florentine

Vegetarian: Roasted Artichokes, Orzo Florentine, Tomato Ragout

Warm Pear Cake, Coffee Ice Cream, Caramel Popcorn

(All with a selection of American red and white wines) Advertisement

Today's report from GCHQ reveals the growing scale of the threat, with more than 80 per cent of large firms in the UK reporting some form of security breach last year, at a total cost of between £600,000 and £1.5million.

Director Robert Hannigan said: 'In GCHQ, we continue to see real threats to the UK on a daily basis, and I'm afraid the scale and rate shows little sign of abating.'

GCHQ is urging all businesses to take greater steps to protect themselves from cyber attacks.

On a daily basis, its agents see computer systems and the information on them being compromised by malicious attackers.

The report says: 'The internet can be a hostile environment. The threat of attack is ever present as new vulnerabilities are released and commodity tools are produced to exploit them.

'Doing nothing is no longer an option; protect your organisation and your reputation by establishing some basic cyber defences to ensure that your name is not added to the growing list of victims.'

The report gives examples of attacks identified by GCHQ, including a previously unknown espionage campaign against the UK energy sector.

Attackers used a technique known as a 'watering hole' attack to distribute 'malware' - malicious softward - into businesses working in the energy sector.

After discovering that a single web design company hosted a number of energy supply sector businesses' websites, attackers added a code to one website which redirected the visiting user's browser to one of three websites controlled by the attackers. GCHQ believe that these watering hole attacks were part of a continuing commercial espionage campaign against the UK energy sector.

The world was shaken after North Korea's apparent hack of Sony, which made The Interview (above)

WE NEED RAPID RESPONSE TEAM FOR EBOLA, SAYS CAMERON David Cameron last night urged Barack Obama to help create a rapid response team of specialists to stamp out outbreaks of ebola and other deadly diseases before they can spread across the world. Over dinner in the White House, the two leaders were updated on the latest infection rates in Sierra Leone. They also discussed the idea of having a standing army of epidemiologists who could be deployed quickly to any area of the world – to assess emerging epidemics and offer swift advice about how to overcome them. Advertisement

Fortunately, agents detected the attack and was dealt with before it could affect the targeted businesses.

In another attack, a technique called 'spear-phishing' was used to attack a high profile organisation. An email was sent to a targeted individual containing an attachment with malicious software.

The attacker was then able to access information about the company's wider network and sensitive informatiob.

The report says attackers range from cyber criminals interested in making money through fraud or sale of valuable information to industrial competitors and foreign intelligence services, interested in gaining an economic advantage for their companies or countries.

In other cases, 'hacktivists' may seek to attack companies for political or ideological motives, or just to show they can.

The worst case scenario would be a rogue state or terrorists using cyber attacks as a form of warfare.

Chief executive of cyber firm Darktrace Nicole Eagan said: 'The growing frequency and sophistication of cyber attacks underlines that we are in a new era of cyber-security.

'Unfortunately the old systems just don't work, whether that's individual countries trying to deal with the cyber threat alone or whether it's organisations thinking they can keep intruders out of their networks.