Prime Minister Gordon Brown hailed London 2012 as an important "job creator and growth generator" in the face of the economic downturn.
As he toured the Olympic Park in east London, he said about 30,000 people will have worked there by 2012.
"On top of all that, there will be 50,000 jobs permanently created as a result of the facilities the site will make possible for the future," he said.
The job announcement comes as work on the site reaches its halfway mark.
"We are ahead of schedule - 3,000 people have already been employed, 11,000 next year and in total about 30,000 people will have worked here by 2012," he said.
"It is a huge employment generator and job creator for the future."
Skill legacy
Mr Brown was joined on his tour of the Stratford site by Olympic Delivery Authority (ODA) chairman John Armitt, London 2012 chairman Lord Coe, and Olympics Minister Tessa Jowell.
They were accompanied by 1,500m runner Lisa Dobriskey, whose father Mike works in construction and helped clean up the site.
Earlier, Ms Jowell said Britain needed the 2012 Games.
We are delivering vital business, jobs and training opportunities in a tough time for companies and workers
ODA chairman John Armitt
"The investment of �6.1 billion in east London is precisely what east London needs, what London needs, what the country needs at this time because it is creating jobs," she told the BBC.
"One out of 10 of all the people working in the Olympic park are either an apprentice or they are people who are being trained, therefore leaving a legacy of skill."
BBC political correspondent Reeta Chakrabati said the prime minister would want to make it clear the Games were part of his economic recovery.
"The cost tripled from the original bid from around �3bn to �9bn," she said. "There are many people who say this is something the country can ill-afford."
'Good progress'
The ODA said the current workforce of 3,315 would increase dramatically during 2009 as the pace of building work accelerated.
Jobs created this year will include bricklayers, wood workers, electricians, security guards, engineers, plumbers, scaffolders and machine operators, as well as administrators and support staff.
At present, the ODA says nearly a quarter of employees are from east London and 57% are from the capital as a whole.
Almost one in 10 were previously unemployed, while the same number again are trainees or apprentices.
The main Olympic Stadium is beginning to take shape
The ODA also says it is creating 250 new apprenticeships on top of an existing 2,000 already planned.
ODA chairman John Armitt said good progress was being made, with the Olympic Stadium taking shape and the first venue - the sailing facilities in Weymouth and Portland - completed.
"We are also delivering vital business, jobs and training opportunities in a tough time for companies and workers," he said. "Maximising apprenticeships on the Olympic Park is an important boost to this legacy."
The ODA also announced that a scheme to help unemployed people in the host boroughs has so far provided more than 300 with training and jobs.
And a programme specifically aimed at helping women get construction jobs has placed about 40 so far.
Lord Coe, chairman of the Games' organising committee, said: "At this halfway point, we are exactly where we want to be - and in some cases, ahead of schedule.
"This is a large and complex project and we don't have a day to waste, but I'm delighted with the progress the teams have made to date.
"We have lots of hard work ahead, but we will be ready, and we won't disappoint."
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