The authorities say Pakistan has the highest number of drug users in the world

It is perhaps the bright colours, the vibrant clothes that make the pictures even more shocking. Or perhaps it is the images of lives disrupted, lives destroyed.

I'm being shown a series of pictures of life on the streets in Pakistan. This isn't for the tourist brochures or company report - this gives a graphic reality to the country's growing drug problem.

It is hard to know which of the images is the most painful to look at.

It could be the one of the "street doctor" who is paid to find a vein by the junkies, about to earn his next payment from the emaciated but desperate man standing above him.

Or maybe it is the group of people, openly injecting themselves, oblivious to anything but their burning need for the next high. Or it could be the body of the man, ignored, abandoned and decaying.

It estimated there are half a million people who inject heroin in Pakistan, and maybe five million drug users in total.

Ruined lives

Iftikhar Ahmed was once a drug addict, injecting heroin to get high. The 26-year-old was confronted by his father, who told him of the disgrace he was bringing on his family.

'Street doctors' are often used by the addicts to get their fix

Iftikhar earned enough as a tailor to finance his habit, and when money ran short, he sold possessions like his video camera.

"After the high had worn off, I would wake up and realise what I'd done, but it didn't stop me," he said.

Until one day on the streets, he was approached by an outreach worker from the country's biggest rehabilitation programme, Nai Zindagi, or New Life. 

And now in the warmth of the late winter sun, in the hills around Barakoh, he is preparing the ground for his vegetables.

He's been here 15 days. He's clean and looking to going some way to restoring the family honour: "I have nothing in my life but regrets. I never took a stand. I spent my whole life high. I wasted myself, I wasted time.

"But I don't regret this as much as I regret bringing shame to my family. God willing, I'll pay them back. Nai Zindagi picked me up off the street. We were worse than stray dogs. I'm very grateful to them for lifting me up from the ground to the sky. Now I'll live this new life in their name," Iftikhar said.

Road to recovery

The farm programme where he works is a key plank in Nai Zindagi's operation.

Aid workers warn that not helping addicts could leave them open to 'recruitment for terrorism'

It gives clean needles to addicts to stop the spread of HIV, it gives advice on health issues, treats wounds and abscesses, and gives addicts the chance of getting clean.

First they travel to a detoxification centre, and when they are done, many of the lucky ones are given the chance to work on the farms.

Money raised here is poured back into the system. The addicts are shown how to grow vegetables, tend their crops and increase their yield. They must stay two months; they can stay up to three.

When they leave, they are given the chance to run their own little patch of ground and sell anything they grow.

Kaleem Amir helps the addicts when they arrive. As a former addict, he knows what they are going through. He was picked up by the outreach workers in Lahore and went through rehabilitation and four years later he is clean and now helping the charity that helped him.

"It helps when they walk through the door to get motivational force from the senior people that were also in the same conditions days, weeks or months ago," he said.

Plenty of victims

Tariq Zafar, the founder of the programme, is a tall man with a grey beard which is beginning to win ground in his darker hair. He too is a former addict.

"It started when I was in college," Zafar said.

Zafar gave up because the initial excitement of the high, the enjoyment of the hit soon gave way and he realised what lay ahead.

With the help of his family he quit and decided to do something to help others who didn't have the backing of supportive parents.

He realises Pakistan is facing problems on many fronts, but he sees the war on drug addiction as a long one, with the potential of many casualties.

"Terrorism is a different thing, this is an epidemic. If we do not respond to increased drug use in the country, and now people being infected with HIV, a lot of people are going to be angry about the fact that they have a disease they were not informed about.

"A lot of people are going to be disillusioned with life and you might have a group of people who you could recruit for terrorism," he said.

The authorities say Pakistan has the highest number of drug users in the world.

This is a battle which at the moment has little publicity, little funding but plenty of victims.