Ai Weiwei, the artist and government critic who emerged last week from nearly three months in police custody, has been asked to pay $1.8 million Cdn in fines and unpaid taxes by the Chinese government.

Pu Zhiqiang, a lawyer retained by Ai's design company, said he has filed a request for an administrative review before the tax authorities.

Ai has been under a gag order and is unable to speak to the media, but his mother told reporters two tax bureau officials came to his studio on Monday with documents claiming the company owned by his wife, Beijing Fake Cultural Development Ltd., owed nearly $760,000 in back taxes.

The officials also demanded an additional $1.1 million in fines. Ai's mother says he refused to sign the documents.

Ai was released from prison last week after confessing to evading income taxes, according state media.

International supporters of the artist believe he is being prosecuted because of his reputation  as an outspoken critic of the Chinese government. Ai had a role in designing Beijing's Bird's Nest Olympic stadium and has exhibited his work in London, New York and Berlin.

China arrested many dissidents this spring after online calls for protests similar to those in the Middle East and North Africa began to circulate. Many have yet to be released.

Pu said Wednesday that it would be difficult to fight the tax charges because authorities have seized all of Ai's financial records. Ai's accountant was arrested in April, about the same time as the artist, who was prevented from boarding a plane to Hong Kong on April 3.

Chinese authorities say the accountant is no longer in detention, but Pu claims his whereabouts are unknown. Authorities also have accused Ai of destroying financial documents.

Beijing Fake Cultural Development is held by Ai's wife, Lu Qing, and the family says Ai is not responsible for its operations. The family also denies taxes are owing.

Under the terms of his bail, Ai cannot travel out of Beijing and must co-operate with an investigation into his affairs.

One of his supporters,  Liu Xiaoyuan, has begun a campaign on Twitter to help Ai raise the money he reportedly owes, according to the New York Times.

"Ai Weiwei has almost 100,000 followers on Twitter," Liu is reported as saying. "If each of them donated a 100,000th of the total amount, we could help him to pay off the fine."

With files from the Associated Press