He put that down to Ms Collins influence with the unnamed Chinese border control official she dined with at a dinner in Beijing late last year arranged by Oravida's bosses Stone Shi and Julia Xu.
"I would have thought that was drawing a very long bow", Ms Collins told reporters on the way into the House.
This afternoon's session began with a personal statement from Ms Collins clarifying her statement two weeks ago when she said she hadn't spoken with Ambassador to Beijing Carl Worker about the dinner.
As she revealed to the Herald two week ago, Ms Collins told Parliament this afternoon she had actually spoken with Mr Worker afterwards, telling him nothing of note had taken place at the "very nice and very short"dinner.
Ms Collins faced three primary questions, the toughest being from Mr Robertson who quizzed her on why a scheduled business and legal roundtable event in Shanghai during her trip was replaced with a visit to Oravida's offices.
Over a month ago, Ms Collins told Parliament that when she was in Shanghai that day, "The only other choice was to go to the airport or to go to Oravida and then to the airport".
Ms Collins said Mr Robertson was wrong to suggest she'd had the roundtable event removed so she could visit Oravida.
The event was on a draft intinerary prepared by MFAT, it did not go ahead, "but it was not at my request".
Her answer was interrupted by Labour MP Trevor Mallard who interjected with a suggestion her family had received "half a million dollars" from Oravida.
Ms Collins' husband David Wong-Tung is a director of Oravida and Mr Mallard later explained the figure he mentioned was based on the fact Mr Wong-Tung was also on the board of four other related companies.
Ms Collins took exception and asked for Mr Mallard to withdraw his comment. When asked to do so by Speaker David Carter, he refused and was ejected from the chamber.
Drawing from a series of emails regarding Ms Collins' China trip released last week by MFAT, Mr Robertson also claimed the ministry prepared a briefing on the unnamed Chinese official she dined with, which he said undermined her claim it was a private dinner.
Ms Collins denied she had been briefed on the official. She has previously said that while her staff asked MFAT for a briefing, she said it was not required when she found out about it.
Ms Collins' final questions came from NZ First Leader Winston Peters who became frustrated at her answers and resorted to asking her about why she would not be in the House on Thursday and early next week, "rather than staying to do the job she's being paid to do".
"That member seems to know more about my diary than I do", Ms Collins replied.
Ms Collins - who still has the backing of Prime Minister John Key - will face further questions tomorrow before going on a break.
Read more of the Herald's coverage of Judith Collins today:
• Judith Collins loses another media battle
• Oravida's milk got preferential treatment in China - Labour
• Judith Collins to stay off Twitter: 'It's not a good space to be'
• New claims as Collins steps back
• John Armstrong: Pushing drama aside may be hoping for too much
Oravida's milk got preferential treatment in China - Labour