Robert Yeldham is leaving local government in the summer to be director of communications at the UK Border Agency (UKBA). The Government hopes that the new body will further protect the UK against illegal immigration and terrorism.
The UKBA is set to launch this month, and will combine the work of the Border and Immigration Agency, UK visas and the border-related work of HM Revenue and Customs.
The new body is expected to have a 250,000-strong workforce, according to Downing Street.
Prime Minister Gordon Brown announced the body last July, shortly after replacing Tony Blair.
It will apply controls at points of entry and exit on people and goods, into and out of the UK, as well as working throughout the world.
Most notably, it will have powers to detain people on suspicion of criminal activity including terrorism.
This week, a leaked Home Office report revealed that hundreds of illegal immigrants are working in care homes in Britain, including a murder suspect from the Philippines.
Lewisham has not yet found a successor to Yeldham, who joined the council in 2005.
He was previously based at the Greater London Authority (GLA), where he advised Labour Party assembly members on communication and policy issues.
Before joining the GLA, Yeldham was a Labour Party press officer, where his work included campaigning for Frank Dobson's unsuccessful London mayoral bid.
Lewisham Council is currently undertaking a review of the Metropolitan Police Authority's communications function, including strategy, planning for external and internal comms, as well as online comms (PRWeek, 28 March).