"The London Legacy Development Corporation will be directly accountable to Londoners through the mayor," said a spokesman.
"It opens for business on 1 April 2012 and will continue the work of the Olympic Park Legacy Company (OPLC).
"The OPLC will be absorbed into the new group along with its board, staff, assets, projects and all undertakings, after which it will be dissolved."
A key goal of the existing OPLC was to create a new park that built on the capital’s tradition of parks such as St James’ and Hyde Park, he said.
The new corporation will have planning and compulsory-purchase powers and will be directly accountable to the London mayor rather than central Government.
It will differ from its predecessor in having a wider remit, with a stronger focus on regeneration, he added.
"Its core task will be opening and operating the Queen Elizabeth Olympic Park. But it will also have power to set planning policy and take planning decisions.
"As a statutory body, the new group will have new duties regarding openness with board meetings. Decision-making committees will have to take place in public."
Johnson said: "Building on the momentum already created by the Legacy Company we are on track to grasp a unique opportunity to harness the Olympic legacy."
Baroness Margaret Ford, chairwoman of the Olympic Park Legacy Company, will become interim head of the new organisation until after the games.