The mining projects had all been approved at state level. Mr Burke's signature was seen as the final obstacle to development.

''Of all the decisions I have ever made, this is the one where I have the least idea of whether the projects are going to go ahead,'' he said. ''For all three projects there are substantial issues.''

Some of the hurdles yet to be overcome are the preservation of a ''biodiversity corridor'' in the Leard Forest to allow koalas and other vulnerable animals to survive, high quality offsets to partially compensate for sections of the forest which would be cut down, and a hydrogeological survey around Gloucester.

Mr Burke compared Monday's decision to the approval granted by former environment minister Malcolm Turnbull to the proposed Gunns pulp mill in Tasmania. That process involved a series of separate ''modules'' that stretched the approvals process out for years, before the project was finally canned.

Asked if his coal and coal seam gas decisions then amounted to ''Clayton's approvals'', Mr Burke said: ''It's a completely fair criticism. I would have much preferred to do things in the usual way, and give clear approvals or rejections. Unfortunately the NSW government chose to leak commercial information, and caused this process.''