Outsourcing giant Serco has renewed a five-year contract with an Australian government agency to provide on-shore immigration detention servicesThe contract, which takes immediate effect, has an approximate value of £1bn, according to the the country's Department of Immigration and Border Protection (DIBP).That sum is subject to the volume of work performed as measured by the number of people being looked after.Serco said in a statement that the current value is below the potential value which may be reached. In its first year it is expected to generate between £100-£150m in sales.In addition to the initial five-year period, there are two extension options of up to two years each available.Serco employs over 2,000 people to service that contract, which in mid-2013 saw it supervise 10,000 detainees. However, actions taken by Australia since then have reduced the number of people in Serco's care to approximateloy 3,000.As of 09:25 shares in Serco were rising 6.82% to 175.5p.