Sean Dwayne Louw, 31, of Hartley Street, Morley, was part of the UK end of the international conspiracy, which targeted South Africans coming to the end of their legitimate visas.

For a fee of between £750 and £900, the gang told visitors they would be "fast-tracked" to an extended visa by a contact in the Home Office. In fact, bogus stamps were used to endorse the visas.

Louw, who acted as a "middle man" in the operation from the beginning of 2006, was jailed for three years at Kingston Crown Court on March 6 this year, after pleading guilty to conspiracy to facilitate the commission of a breach of immigration law.

He asked Mr Justice Simon and Mr Justice Royce, sitting at London's Criminal Appeal Court, to reduce that sentence, claiming it was too harsh.

Louw argued he should have been handed a lesser sentence as he pleaded guilty and had given information to the police about other people involved in the plot.

But, refusing his application for permission to appeal, Mr Justice Simon said: "The aggravating factors included the fact that this was a well organised and sophisticated conspiracy involving repeated offences over a significant period of time.

"He contends that he received insufficient credit for his guilty plea and the assistance he gave. He was a man of previous good character.

"But this was subversion of the immigration rules by the production of false visas which were produced for the offenders' own gain. In the circumstances a sentence of three years was not excessive and this application must be refused," the judge concluded.