Ai Weiwei -- a dissident Chinese artist and political activist who spent 81 days in detention after being arrested by Chinese authorities in Beijing in 2011 -- was refused a six-month business visa by British authorities, who allegedly claimed he had lied on his application form. A statement posted through his Instagram account said the British government had instead issued him a 20-day entry visa.

“It is a matter of public record that you have previously received a criminal conviction in China, and you have not declared this,” the British embassy in Beijing told Ai, according to a copy of an official letter posted by the artist via Instagram. “Exceptionally, it has been decided to grant you entry clearance outside the immigration rules for your stated dates of travel to the U.K.

“While an exception has been made in this instance, any future application you submit must be completed as accurately as possible,” embassy officials wrote in the letter -- which bears the signature of an entry clearance manager at the U.K. Visas and Immigration department -- adding Ai might face a 10-year ban if he did not comply with the visa rules.

However, according to a separate Instagram post, Ai has "never been charged or convicted of a crime” and that the decision to deny him a business visa was made despite attempts to “clarify this claim with the UK Visas and Immigration Department and the British Embassy in Beijing over several telephone conversations.”

In 2011 -- when he was held in secret detention by Chinese authorities during a crackdown on activists critical of the government -- Ai’s passport was confiscated. He was also fined 15 million yuan ($2.4 million) for tax evasion in a civil case in 2012, a move he claims was politically motivated. 

Ai’s passport was finally returned to him last week, allowing him to travel abroad for the first time in four years. However, his short-term Schengen visa does not allow him to enter the U.K.

The lack of a business visa may prevent Ai from attending “ his exhibition installation and opening at the Royal Academy of Arts in September 2015,” the statement posted through his account said. “This decision is a denial of Ai Weiwei’s rights as an ordinary citizen, and a stand to take the position of those who caused sufferings for human rights defenders.”