Alireza Jafarzadeh claimed that Shiite guerrillas are posing as pilgrims or wounded veterans seeking medical treatment to cross the border.
On reaching Iran, they are schooled in the camps for up to a month in skills such as sniper techniques, bomb building and firing anti-aircraft missiles before being sent back to Iraq.
Mr Jafarzadeh, a dissident who now heads a Washington-based think-tank called Strategic Policy Consulting, claimed the operations have the blessing of top government officials including Mahmoud Ahmadinejad, the Iranian president.
He said: "The Iranian regime is secretly engaged in the organisation and training of large Iraqi terrorist networks in Iran to heighten insecurity and instability and force the coalition forces to leave Iraq.
"We are not talking about some ragtag elements and individuals who go out of their way and happen to provide weapons or assistance to a number of Shia militia groups.
"We are talking about a systematic, well-organised, high-level training officially provided by the Iranian regime."
Mr Jafarzadeh said the Iranians hoped to "pave the way for establishment of an Islamic republic in Iraq".
He claimed to have obtained the information from a network of resistance informants inside Iran.
Mr Jafarzadeh has been credited with the first revelation, in May 2003, of Iran's efforts to develop a clandestine nuclear weapons programme.
Last September, he disclosed that Tehran had revived secret efforts to enrich uranium with laser technology.
At a press conference in New York, Mr Jafarzadeh displayed maps and satellite photos showing some of the purported camps' locations.
They included two near the former shah's palace in Tehran, another south of the capital in Jalil Abad, and another, the Bahonar base in Karaj where, he said, techniques of guerrilla warfare, including deception and intelligence-gathering are on the curriculum.
Other camps, he said, are in Qom, in Isfahan and in Iraq-Iran border areas near Kermanshah, Kurdistan, Ilam and Khuzestan.
Mr Jafarzadeh said Iran's supreme leader, Ayatollah Ali Khamenei, and Mr Ahmadinejad, are closely connected to the training programme.
He named Abu Ahmad al-Ramisi, the governor of southern Iraq's Muthanna province, and two members of Iraq's national assembly as also being secretly involved.
The camps are said to be run by several top commanders of the Qods Force, the most highly trained branch of Iran's Revolutionary Guards Corps, with some members of Lebanon's Shiite Hezbollah militia also taking part, he said.
He said the camps are under the command of Brigadier General Mohammad Shahlaei, a Revolutionary Guards officer.
Officials in the United States have taken a wary view of Mr Jafarzadeh's affiliation in the past with the National Council of Resistance of Iran - which wants to overthrow the country's government.
Its military arm, the Mujahideen Khalq, or MEK, is considered a terrorist group by the US. Saddam Hussein, the former Iraqi dictator, allowed the group to operate camps in Iraq from which it launched attacks inside Iran.
Mohammad Mir Ali Mohammadi, a spokesman for Iran's UN mission, last night dismissed the claims. He said Mr Jafarzadeh was an "official representative of MEK, which is a terrorist group, and even on the terrorist list of the US state department".
Richard Grenell, a spokesman for the US mission to the United Nations, added: "We've expressed our concern regarding Iranian support for Iraqi militants. This meddling only intensifies the conflict in Iraq."
Meanwhile, Tariq al-Hashemi, the Iraqi vice-president, renewed calls for talks to be opened with insurgents in an attempt to bring peace.
However, he excluded al-Qaeda and said the group was "not very much willing in fact to talk to anybody".
• US troops killed five insurgents and destroyed a bomb-making factory north of Baghdad yesterday.
• HOLLYWOOD was yesterday accused of waging psychological war on Iran.
In comments which appeared to be directed at blockbuster movie 300, Mahmoud Ahmadinejad suggested the film was designed to portray Iranians as "savage".
Starring the Scottish actor Gerard Butler, the film depicts a 480BC battle between Greeks and Persians. But many Iranians see 300 as part of a broader campaign to vilify the Islamic republic, which is locked in a standoff with the West over its nuclear programme.
The Iranian president accused film-makers of trying to tamper with history. Mr Ahmadinejad, pictured left, said: "By psychological war, propaganda and misuse of the organisations they have themselves created, and for which they have written the rules, and over which they have a monopoly, they are trying to prevent our nation's development."
Iranian officials, media and bloggers have also criticised the way their ancestors were portrayed in the film, inspired by the tale of 300 Spartans who held out at Thermopylae against a Persian invasion led by Xerxes.