The Home Office is to review every asylum case which involved an employee accused by a newspaper of helping people remain in the UK for cash.
Officials said the man had not approved applications
A spokeswoman said the man had now been suspended but had only worked as an interpreter at the Croydon site and was not able to approve applications.
There was a determination to root out any misconduct, officials have said.
The Sun said claimants were advised to pretend they were from Zimbabwe because of a ban on deportations there.
According to the paper, immigration officer Joseph Dzumbira, 35, from Southend in Essex, said he could provide fake Zimbabwean arrest warrants to support asylum seekers' claims that they would be in danger if they were returned.
Zimbabwe-born Mr Dzumbira, who the paper claimed was himself an asylum seeker who was granted leave to remain in the UK in 2001, has worked at the IND's Lunar House headquarters for seven years.
The Home Office spokeswoman said: "He is not an immigration officer nor does he work in a position of seniority in the Home Office.
"All previous cases in which this individual has had any involvement will be reviewed."
Commenting on the case, Home Secretary John Reid said: "We take all allegations of corruption seriously and we will investigate them.
"Where serious we will refer them for prosecution."
Figures released to Parliament earlier this month show 127 IND staff were sacked for misconduct or failing to do their jobs properly between January last year and May this year.
Reasons for the sackings include poor performance but at least 15 followed allegations of corruption so serious they had to be investigated by the police.
The Home Office said the sackings reflected a determination to root out misconduct and corruption amid the "biggest shake-up" at its Immigration and Nationality Directorate.
But the shadow immigration minister Damian Green said the system is "shot through with incompetence and corruption" and should face a full independent inquiry.