By BBC Moscow correspondent Andrew Harding

Russia is no longer a totalitarian state. But it still locks up more of its own citizens than almost any other country in the world.

There are, right now, about 1m people in prison here, packed into cramped cells in the sweltering summer heat.

Almost a third of them are technically innocent. The wheels of Russian justice run slowly, and hundreds of thousands of people are held for years before their cases even come to court. Precious few are let out on bail.

Tuberculosis has spread through this vast empire like a swarm of flies. The hot, airless, crowded dormitories are the perfect breeding ground for the disease.

Some prisoners have no more than half a square metre to live in. That's enough room to stand, or maybe squat. Sleeping is done in shifts.

Small wonder that today one in 10 people in Russian jails has tuberculosis - for many it is a death sentence.

It is in this nightmarish underworld that Grigory Pasko has spent the last 19 months of his life.

Arrested

The 37-year-old investigative journalist and environmental campaigner was arrested by Russia's Federal Security Services, the former KGB, in November 1997.

His crime was to have uncovered evidence that the Russian navy had been illegally dumping nuclear waste at sea, not far from the Pacific port of Vladivostok.

Video footage which he'd taken was shown on Japanese television - causing a huge scandal. The Russian authorities were not amused.

Pasko was not only a journalist, but a naval officer, writing for a military newspaper.

They threw him in jail, and charged him with espionage and treason. It was a knee-jerk reaction by officials who still seem to believe they have the right and the power to silence all dissent.

A 'cookie'

Amnesty International has named Pasko as a prisoner of conscience

But Grigory Pasko would not be silenced.

Three decades ago, Alexander Solzhenitsyn's descriptions of prison life were smuggled out of the Soviet gulags, copied by hand, and passed furtively around a small, anxious circle of dissidents.

Today, things are a lot easier.

A few weeks ago, an article popped up on the Internet. It was called "cookie" or "biscuit" - slang for a first-time prisoner. The author was Grigory Pasko.

How it got there is not entirely clear. Presumably a handwritten version was given to a visitor.

Pasko's wife, Galina, is understandably coy about the subject - the last time she wrote a critical article about the case, she was barred from seeing her husband for several months.

"Cookie" tells the story of Pasko's experiences in jail, and offers survival tips to those following in his footsteps.

How to survive

"Keep a large bag at home, full of provisions," he writes. "Anyone determined to challenge the authorities can be hauled off to prison at a moment's notice."

He talks about the brutal nurse who used a thick syringe to take a blood sample, and threatened to beat him if he fainted.

He describes the art of keeping clean by using the only source of water - the toilet bowl, and the stench and heat of a communal cell - built for 12, but packed with 40 people.

Pasko advises new prisoners to find a "family" for protection, and to share food parcels with.

Arriving in a new cell one day, he is forced to surrender the arms of his sweater - the wool is used like string to pass messages and cigarettes between cells.

When you're arrested, he warns, remember the war films and "say nothing".

"You have to survive the first 72 hours. They'll beat you and interrogate you. But keep quiet. Eventually they'll have to get you a lawyer."

Publicity

Last week one of Grigory Pasko's supporters visited him in jail in Vladivostok. Alexander Tkachenko said he was amazed to hear other prisoners shouting out at Pasko as he walked down the corridor.

"They were congratulating him," he said. "Thanking him for telling the world outside what life inside is like."

Pasko and his supporters clearly hope the extra publicity will help his case. He has already been named a prisoner of conscience by Amnesty International.

International outrage recently forced the Russian authorities to release another environmental campaigner, Alexander Nikonov.

But after 19 months in jail, Captain Pasko has grown a thick skin of cynicism.

"It's better to forget that you have a family, a home, a car," he writes.