"We won't make a decision until that process is completed," Mr Clifford said today.
It is nearly four years since 29 men died in explosions in the mine on the West Coast.
A staged plan to re-enter the mine and explore the tunnel up to a rock fall about 2.3km in from the mine portal had been approved and the Government had committed $7.2 million to the effort.
Moving into the tunnel or drift was seen as the first step to recovering the remains of the miners.
Bernie Monk, a spokesman for some of the families killed in the explosion, has today expressed dismay over the revelations. A lawyer representing the families had been asked to find out what was holding up the mine re-entry.
The proposal to re-enter the mine has been beset by delays, the latest in August when Solid Energy announced "potentially fatal risks" still needed to be examined before attempting to enter.
The board of Solid Energy also has its directors' liability "at the forefront of their minds", Mr Clifford said.
"Directors' liability is an important thing, and it's been taken very seriously. There's been a fundamental change in the law since Pike River. We need to learn from that, and it's been taken seriously."
The re-entry process was highly complex, he said, citing 600 separate controls that include different procedures, training, and documents put in place before anything can happen. Mines Rescue and WorkSafe have either been part, or been involved in, observing the process, he said.
WorkSafe had been in the twice-monthly meetings with the families, he said, and it was up to them to tell the families, not Solid Energy.
The board has requested legal advice but that is yet to be settled, said Mr Clifford, who started with company in May this year.
"There's no one single issue here, it's a complex project.
"It'll get to a point when we will review that as a company, and get independent advice."
He said Solid Energy was aiming for a final decision by the end of next month - sooner if possible.
Asked if he understood the difficulties families had in the process being dragged out, he replied: "I feel for the families on that front."
Solid Energy was not holding anything back from the families, including any videos or scans, Mr Clifford said."I have not seen anything that the families haven't."
State Owned Enterprises Minister Tony Ryall also said today the decision was ultimately for Solid Energy to make, not WorkSafe.
"The Solid Energy board is ultimately accountable and legally responsible for the safety of people working at the Pike River site and any decisions on mine re-entry are their responsibility, and their responsibility alone," Mr Ryall said.
"I understand people's frustration, but safety has to be absolutely paramount."
The union representing New Zealand coal miners said the re-entry has been mishandled by Solid Energy, and Mr Ryall needed to step in. "The latest revelations suggest that the Board of Solid Energy hasn't been focused on getting the job done," said Ged O'Connell, assistant national secretary of the Engineering, Printing and Manufacturing Union.
"They have the financial resources and the capability ready to go, but nothing's happening. They appear to be sitting on their hands and leaving the Pike River families wondering what's going on.
"In the interests of the families and their community we urge the Minister to direct Solid Energy's Board to make re-entry of the Pike River mine drift a top priority, or hand the job over to someone who wants to do it."