The immigration minister, Brendan O'Connor, has accused the shadow foreign minister, Julie Bishop, of an "unprecedented attack" on the credibility of the Indonesian ambassador in the wake of her comments to the Guardian about Indonesia's attitude towards turning back asylum seekers' boats.

O'Connor said Bishop "must reveal why she accused the ambassador of lying after he publicly ruled out the Coalition's shambolic plan to turn back the boats".

"If Ms Bishop can't explain her comments, she must apologise to the ambassador for calling him a liar," he said.

On Friday the Indonesian ambassador to Australia, Nadjib Riphat Kesoema, said Indonesia would not accept asylum seekers from boats returned under the Coalition's stated policy of turning back vessels when it is safe to do so.

But, in an interview with Guardian Australia published on Monday, Bishop said high-ranking Indonesian ministers and officials had indicated privately that Indonesia would co-operate with a Coalition government to turn back people-smuggler boats.

When pressed on Tuesday over whether the Coalition has an agreement with the Indonesian government to turn boats around Opposition leader Tony Abbott said:

"The policy was to turn around boats where it is safe to do so. We are confident that we can have a strong and constructive relationship with the Indonesian government.

"We do have a lots of discussions with senior members of the Indonesian government. It's impossible for an Opposition to negotiate with a sovereign government but we've had very frank discussions."

Julia Gillard said on Monday that Bishop "embarrassed the nation" by claiming the Coalition had secured support from Indonesia for its people-smuggling policy.

During question time, the prime minister said if Bishop wanted to maximise co-operation in the region, "what you do not do if you are treating our neighbours with respect is give an interview claiming that you have got a deal with them only, when it gets a bit hot and people go inquiring about that deal, to then, in a shambolic way, back away from it".

"But that, of course, is exactly the position the opposition has found itself in. It is in that position because, in this very important area of people smuggling, what it is continuing to do is try and peddle a slogan," Gillard said.

Senior government minister Craig Emerson also criticised Bishop's comments that the Coalition had fixed a deal with the Indonesians to turn back asylum seeker vessels.

"That's an outright lie by Julie Bishop," he told ABC radio.

"The Indonesian ambassador couldn't have been clearer, and that is that they will not co-operate in turning back boats."

When interviewed by the Guardian, Bishop was asked what she knew that others did not to conclude Indonesia would co-operate with the Coalition's policy of turning back asylum seekers' boats.

She replied: "Well I am not at liberty to tell you. I have had a number of conversations with high-ranking Indonesian ministers and officials, as has [the immigration spokesman] Scott Morrison as has Tony Abbott and I am convinced we can work in co-operation with Indonesia to achieve our policy aim."

Asked whether they would take boats back, she replied: "I am confident we would be able to achieve what we did in the past. The fact is they are Indonesian boats with Indonesian crew and I am sure we can work co-operatively with them and … one thing you understand about diplomacy and others do as well is the professional diplomats are paid to present particular views but what goes on behind the scenes can be quite different. What people say privately can be different to what they say publicly, that's why I am devoting my time to quiet consistent diplomatic messaging and relationships."

Guardian Australia contacted Bishop on Sunday to ask her whether Nadjib Riphat Kesoema's comments on Friday changed any of her statements in the earlier interview.

"We don't know the situation ahead of us right now, but no such collaboration will happen between Indonesia and Australia [to] bring back the people to Indonesia," he said.

Bishop said: "I would expect the ambassador to say those things publicly."

She said she had been "selectively quoted" in the article and that she had never claimed the Coalition had an "agreement" with Indonesia, as suggested in Guardian Australia's original headline.