A decision by the government on whether the controversial high-speed rail link between London and Birmingham will get official approval will now not be made until the new year. Transport Secretary Justine Greening has confirmed speculation that an announcement is to be delayed. She explained that she needed more time to analyse the issues raised in a recent consultation.

The HS2 project, if it goes ahead, has a budget of £32 billion, and will shorten the journey time between the two cities to just under 50 minutes. The project has been the focus of opposition by a number of ministers, including those with key roles in the Tory party.

Cheryl Gillan, Welsh secretary and Chesham and Amersham MP, has threatened to step down if the scheme is approved. She has already asked that a tunnel be built in the Chilterns to prevent the rail link from spoiling the countryside. Greening is concerned that if she agrees to the tunnel, which could cost around £500 million, then she will have to consider similar options along other parts of the proposed route.

She told ministers that she would be making no further comment on the project this year, adding that she was giving herself until January 2012 to fully assess the relevant factors.

The project has come under fire from environmental groups. Supporters of the scheme say that it will bring economic benefits to the Midlands. However, those who oppose it say there is little proof that this will be the case and want the money to be spent on improving existing infrastructure.