Allan Leighton, chairman of post group Consignia, said the company would continue making losses of £1.5 million a day for three years.
Mr Leighton said he did not believe the service should be privatised. He was confident his business plan would turn the company's fortunes around.
In an interview today for the BBC Radio 4 On The Ropes programme, Mr Leighton said: "We are losing £1.5 million a day. We can't continue to do that. We will go bust.
"The plan we have in place gets the mail's business back to profit and in terms of cash generation, in three years. In the same way that things don't go wrong overnight, you can't get things to go right overnight."
Mr Leighton said he personally was not a fan of privatisation.
He added: "I'm prepared to say in my time-scale we will not see the Post Office privatised."
Mr Leighton was also questioned about his reputation for being ruthless.
He said: "I've never had to make a decision to make 30,000 people redundant before.
"I don't ever want to do it again. It impacts people. It impacts people's families."
Last month Consignia was consigned to history as the group's name and 17,000 jobs and second deliveries were axed in a bid to reverse record losses.
A pre-tax loss of £1.1 billion for the last financial year was reported, including operating losses of £318 million, about £1.2 million for every working day.
The group announced it would be renamed Royal Mail at a cost of about £1 million, compared to the £1.5 million spent on launching Consignia 15 months previously.
The interview will be repeated on BBC Radio 4 at 9.30pm.
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