Julia Gillard was 'graceful' when Bill Shorten called to tell her she'd lost his support

BILL Shorten told Julia Gillard over the phone that she had lost his support, in what he describes as a painful decision.

Rudd and Shorten

BILL Shorten broke the news to Julia Gillard by telephone that she had lost his support, in what he describes as a painful decision that has cost him lifelong friendships.

The man who wants to be Labor leader and prime minister one day has now played a role in cutting down the past two Labor PMs, earning him the nickname "Bill the Knife".

Some people are calling him a "rat" or "turncoat" for switching his support to Kevin Rudd.

One MP said Mr Shorten "would forever be known as someone who knifed two prime ministers in three years".

One of his friendships under enormous strain is with Paul Howes, a co-conspirator and "faceless man" in the 2010 coup against Mr Rudd.

Mr Howes heads Mr Shorten's former union, the Australian Workers Union, and backed Ms Gillard.

"Some friends won't be my friends any more," Mr Shorten told the Herald Sun. "Some people will so disagree with what I believe in my heart of hearts, that they won't like me any more.

"Some people will say unkind things, but what I realise is you've got to be true to yourself above all else. I hoped it wouldn't get to this."

For weeks, despite a widespread belief his support for Ms Gillard was wobbly, Mr Shorten repeatedly pledged it, including just hours before the vote.

A visibly exhausted Mr Shorten said he had been talking to people in his electorate for "two to three weeks" about the leadership and found voters had "switched off" from Ms Gillard.

He said he made up his mind only after Ms Gillard called the spill and Mr Rudd said he would stand.

Incongruously, he decided the best way to protect Ms Gillard's legacy - such as carbon pricing, the National Disability Insurance Scheme and education changes - was to switch to Mr Rudd.

"It's sad. Only she could have accomplished what she's accomplished, yet it is he who is the most likely to protect what she has accomplished," he said.

"I don't know how to give up. To do nothing would be, in my opinion, giving up."

At 6pm on Wednesday, an hour before the leadership showdown, Mr Shorten telephoned Ms Gillard.

"I indicated, after three years of very strong support, I felt that Kevin Rudd would give the Australian nation and people who believe in the Labor cause the best choice," he said.

He said Tony Abbott would have won control of the Senate as well as the House of Representatives.

"I wasn't evaluating her as a person. I was saying we're more likely to win and to provide the strongest possible alternative to the Coalition."

He would not reveal what she said. "She was courteous and she was graceful."

He then rang Mr Rudd.

Mr Shorten said he did not seek any personal gain for his support.

Having been one of the strongest critics of Mr Rudd, he said he now believed the man he helped axe had changed.

"He certainly demonstrated to me that he would be a more consultative Prime Minister, and he said that he had learned a lot in the last three years."

Mr Shorten conceded his five years in politics had been bruising. "Do I think I've made mistakes along the way? Absolutely."