Gordon Brown hailed the Olympic project as an important "job creator and growth generator" in the face of an economic recession.
The Prime Minister toured the Olympic Park in Stratford, east London, to mark the halfway point from July 2005, when London won the right to host the Olympics, to the opening ceremony of the Games in 2012.
He said: "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. It is a huge employment generator and job creator for the future."
He added: "On top of all that, there will be 50,000 jobs permanently created as a result of all the facilities that the Olympic site will make possible for the future."
Mr Brown was joined in his tour by Olympic Delivery Authority chairman John Armitt, London 2012 chairman Lord Coe, Olympics Minister Tessa Jowell and 1500m runner Lisa Dobriskey, whose father Mike works in construction and helped clean up the site.
Mr Brown said: "The number of jobs is moving up very, very quickly and it is a good sign in what is a difficult global economic situation. It is a job creator and a growth generator and will also be a huge sporting achievement."
The focus of the visit was very much on jobs, with the announcement of new commitments to increase apprenticeship numbers by 250 and for ODA contractors to commit 3% of the Olympic Park workforce to be apprentices. There is a target of 2,000 trainees. But the economy, and how it will hit the £9.3 billion project, was not far from everyone's minds.
Private funding for the Olympic Village and media centre is being hampered by the credit crunch.
On the village, Mr Armitt said: "On the private sector money, we are still in discussion with the banks and investors and we remain confident that we will be able to do a deal this year. In the meantime, we will be releasing funds within the budget to make sure that we stay on track.
"With the media centre, we want to start construction on that in April and I'm sure that we will. In the current economic climate, we are one of the projects that is not being delayed for other projects and we are getting people to work."