Four people who ran a bogus college and corrupt immigration advisory firm have been jailed for a total of 25 years for masterminding an immigration scam that is thought to have netted them millions of pounds.

The four were all arrested after a joint investigation by the UK Border Agency's immigration crime team and Metropolitan Police. Chinese nationals Junjie Kao (30), Wie Xing (30) and Bangladeshi national Khaled Mahmud (35) pleaded guilty to conspiracy to assist unlawful immigration. All three were sentenced to seven years imprisonment.

Tareq Mahmud (35), also a Bangladeshi, was found guilty after a trial at Croydon Crown Court and was sentenced to four years imprisonment. Junjie Kao and Wei Xing also pleaded guilty to money laundering after £2.65 million pounds in cash was discovered by UK Border Agency officers underneath their bed in the flat they shared in Rotherhithe, south east London. They were sentenced to a further four years each, to be served concurrently.

The UK Border Agency will now seek to deport the four from the country once their sentences have been served.

At the heart of the gang's conspiracy was a bogus college which they set up, purporting to offer genuine courses of education, but in fact offering none.

For payments sometimes amounting to thousands of pounds, the gang provided fake documents and certificates to allow their "clients" to gain visas to stay in the UK.

The gang also set up a legal services company, which claimed to provide advice to students from China and the Far East who wanted to extend their visas, and helped prepare immigration applications which were then supported by the false documents they had manufactured.

The whole operation is thought to have netted them in excess of £4.5 million. £2.65 million in cash was discovered stuffed into boxes, suitcases and bags in a room shared by Kao and Xing during a raid on their home by UK Border Agency officers.

UK Border Agency Regional Director, Tony Smith said:

'The tough sentences handed down today demonstrate our determination to tackle those who commit organised immigration crime and bring the perpetrators to justice. Those behind this conspiracy showed total disregard for the law, and their motives were purely financial.

'We will continue to work shoulder-to-shoulder with the police and other enforcement partners to identify criminal activity and stamp out any abuses of the system.'

Detective Superintendent Chris Foster, Head of the UK Border Agency's London and South East Region Immigration Crime teams said:

'The UK Border Agency, working with the Metropolitan Police, will continue to work in partnership to identify, dismantle and disrupt criminal networks who are involved in or benefiting from immigration crime.

'This was an extremely complex 18 month investigation that involved many thousands of pages of documentary evidence seized from a bogus college and a corrupt law firm.

'The amount of cash seized from underneath the bed of the defendants only highlights the attraction that immigration crime has for criminal gangs. A financial asset stripping investigation is ongoing.'

The UK Border Agency will now seek to deport the four from the country once their sentences have been served.