The architects of the original Tokyo 2020 Olympic stadium have accused the Japanese government of putting the legacy of the Games in jeopardy and overlooking several designers after it unveiled two new plans for the arena.

The Japan Sports Council has shortlisted two designs for the stadium - Design A and Design B. One of which will be selected as the blueprint for the 80,000-capacity structure.

Although the council declined to identify the contractors behind the designs, reports in Japan have indicated that one proposal was submitted by Taisei Corp, while the other was put together by a joint venture involving Takenaka Corp, Shimizu Corp and Obayashi Corp.

British-based architects Zaha Hadid, who were originally lined up to take on the project, said that they were “restricted” from bidding again as were “many other Japanese and international architects and contractors”.

A statement made by the firm also batted away suggestions that its own design had contributed to costs spiralling over budget. In July, Japanese president Shinzo Abe withdrew the plans drawn up by Zaha Hadid, citing budgetary factors.

“Work would already be underway building the new National Stadium in Japan if the refinements proposed by Zaha Hadid Architects and our Japanese design partners over the previous years had simply been made to the original competition-winning design, avoiding all delays,” said a Zaha Hadid spokesperson, adding that the design met “all the requirements of the new brief” and would have been ready for the 2019 Rugby World Cup.

“There are now serious risks of a rushed process, with no certainty on the likely construction cost of the stadium, and that it may not be ready in time or deliver a significant sporting legacy without expensive conversion after the 2020 Games.”

The Japan Sports Council has indicated that the expected completion date for both proposals is 30 November 2019. Both the designs in question have a construction budget of ¥153bn (US$1.26bn, €1.14bn, £832m), putting them within the council's ¥155bn (US$1.28bn, €1.16bn, £848m) budget.