Auckland: Tonga is slipping into a high-level political crisis after revelations its diplomatic passports have been sold to Chinese nationals on the express order of the island nation's prime minister.

The issue is splitting the already divided royal family, with King Tupou VI ordering that passports not be sold - but the Queen Mother insisting they be given to her Chinese friends.

Diplomatic passports give holders special high-security access in many airports around the world.

Auckland would be the first place they would be used.

Tonga has had a long history of selling citizenship and passports. In the 1990s it gave them away to runaway despots such as Ferdinand Marcos, of the Philippines, and his family, Hong Kong criminals and Libyan and Palestinian nationals.

Tongan news website NZ Kaniva Pacific says the king told Prime Minister Siale'ataongo Tu'ivakano not to issue passports to a Chinese national, Sien Lee, and his wife.

However, in Tonga the real power rests with the Queen Mother, Halaevalu Ahome'e, and she ordered the passports be given to her friends.

Kaniva says the prime minister then told the Ministry of Foreign Affairs to issue the passport  or face consequences.

It says it is the fourth diplomatic passport given to Mr Lee.

Kaniva said it had obtained emails from Foreign Affairs Secretary Mahe 'Uli'uli Tupouniua who told staff of the prime minister's involvement.

"I suggest we abide by his direction at this stage as he made it very clear to me yesterday that we take action or else."

Another official commented in emails: "I'd hate to be around when HM Tupou VI finds out."

Tonga's Audit Office has also warned that the practice of giving diplomatic passports is unacceptable "and puts the country's reputation at risk and should be discontinued immediately".

Fairfax NZ News