Keith and Anne Bird, a retired couple from Basingstoke, Hampshire, were waiting to board the same plane.

Mr Bird, 66, said: 'I have no problem at all. There is so much intrusion into our lives these days I think that walking through the scanners will be like water off a duck's back.

'In some ways I prefer it to the amount of CCTV there is because it serves a definite purpose - to protect people.

'You don't see people marching in the streets about this - it really is not an issue.'

A BAA security officer demonstrates the new scanners at Heathrow Airport today

His 65-year-old wife agreed. She said: 'I don't see any problems with having my body scanned. Anything that makes flying safer is a good thing.'

Edward Smith, 38, was flying to Singapore this evening.

The business consultant from Blackburn in Lancashire said: 'Measures such as these are vital because terrorists do not play by the rules.

'We must use every piece of technology possible to disrupt them and prevent them from creating more atrocities.'

But Alex Deane, a barrister and director of campaign group Big Brother Watch, said such measures meant 'the terrorists have won'.

'People are understandably afraid of terrorism,' he said. 'But we didn't allow the IRA to impede our freedoms or change our way of life, and we shouldn't change now either.

'Those upset by the prospect of undergoing these scans shouldn't be forced to choose between their dignity and their flight.

'What kind of a free society does the Government think it is "protecting", when it invades our privacy like this?

'When we are forced to expose ourselves at the airport in order to go on holiday, the terrorists have won.'

The image from the scanner is displayed on a computer screen, as seen below

Timothy Kirkhope, Conservative leader in the European Parliament, said an 'urgent' debate was necessary in Westminster and Brussels on the scanners and the manner in which they were being introduced at airports.

He said: 'Body scanners are being brought in without adequate public or parliamentary consultation both in Brussels and Westminster.

'Whilst I am not against their use and the need to give security to travellers, I have concerns about the 'bull in a china shop' approach currently being adopted and promoted by the UK Government.

'Who pays for these machines? The airports and the Government have yet to agree.

'We are also alienating more and more passengers, and drawing flak from civil liberties groups without having had the opportunity to debate the efficacy of the proposed body scanners or how they are to be used. This is unacceptable.'

As the technology was implemented at Heathrow's Terminal 4 and Terminal 2 of Manchester Airport today, Transport Secretary Lord Adonis today sought to allay privacy fears.

The scanners were introduced at Heathrow and Manchester airports yesterday, sparking outrage among campaigners. These new warning signs have been installed to make passengers aware of the changes

The Cabinet Minister said the images from the scans are deleted 'immediately' and staff carrying out the procedure are fully trained and supervised.

Lord Adonis likened the scans to the current pat-down travellers are subject to at airport security gates.

'A pat-down search is a pretty intrusive procedure but people accept that because it is important that we do detect whether there are weapons or other powerful substances that people may be carrying,' he said.

'A body scanner is in the same category - it is very important to stress that the images which are captured by body scanners are immediately deleted after the passenger has gone through the body scanner.

'Staff are, of course, properly trained and supervised who manage the body scanners.'

Lord Adonis also stressed that passengers would not be selected 'on the basis of personal characteristics'.

He said there would be a consultation on the use of scanners, but added that there was an immediate need to begin using them following the attempted Detroit bomb attack on Christmas Day.

Umar Farouk Abdulmutallab is accused of trying to detonate a bomb on a flight as it was about to land in the U.S. city.

Lord Adonis today sought to allay privacy fears over the introduction of full body scanners

'Given the current security threat level, the Government believes it essential to start introducing scanners immediately,' he said.

'However, I wish to consult widely on the long-term regime for their use, taking full account of the experience of the initial deployment.'

A spokesman for BAA said that all passengers on all flights may be subject to the scan and that they would be randomly selected. 

Birmingham Airport will have the scanners installed later this month ahead of a national roll-out.

Heathrow Terminals 1, 2, 3 and 5 will see the scanners implemented in the next few weeks.

A Department for Transport spokesman said: 'We understand the concerns expressed about privacy in relation to the deployment of body scanners, which is why we have drawn up a code of practice for their use.

'This will ensure operators are separated from the passengers being screened, and these anonymous images are destroyed after scanning is complete.'

'This code of practice also makes clear that passengers will not be selected for screening on the basis of gender, age, race or ethnic origin.'

The security director of BAA said the seven-second scans were a 'significant' move towards protecting airports against terrorist attacks.

Speaking at Heathrow today, Ian Hutcheson said: 'The security and safety of our passengers and staff is BAA's first priority.

'The introduction of full body scanners and other technology is one significant step towards a more robust defence against the changing and unpredictable threat posed by terrorists.

'However it is important that, as a country, we make better use of the intelligence available to industry and Government and continue to promote the close assessment of passengers' behaviour.

'Only by doing so will we build a robust security system that is dynamic enough to respond quickly and effectively to the emerging threat.'