The embattled Mrs Bishop had been planning to travel to the United States for an international summit of parliamentary speakers in New York at the end of August.

It is understood planning for the trip was well advanced, but Mrs Bishop quietly withdrew her travel plans in the wake of public fury over her travel expenses at home and abroad.

"The Speaker was considering travelling to New York for that meeting but she has since decided not to," Mrs Bishop's chief of staff and spokesman Damien Jones confirmed.

Asked when the decision was made, Mr Jones said: "In recent times."

Fairfax Media understands the decision was made in the past few days. Plans for the trip had not yet been sent to Prime Minister Tony Abbott's office for approval but if  they had,  they would have been rejected.

Mrs Bishop has also cancelled plans to visit Canada around the same time.  She had been planning to take up an invitation from the National Assembly of Quebec.

"That would have been no cost to the taxpayer but we've similarly decided that is not a priority," Mr Jones said.

Mrs Bishop will be conspicuous in her absence from the World Conference of Speakers of Parliament at the United Nations HQ in Manhattan. An estimated 130 Speakers from around the world will attend the conference,  which is billed as a "unique forum for dialogue and co-operation between parliaments at the highest level".

The controversy surrounding Mrs Bishop began more than two weeks ago when it was revealed she spent $5227 of taxpayers' money to charter a chopper to fly from Melbourne to Geelong for a Liberal Party fundraiser last year.

It subsequently emerged she had spent massive amounts of taxpayer money on overseas travel, chartered several other flights and claimed travel allowance to attend the weddings of Coalition colleagues.

Mrs Bishop has pledged to pay back the cost of the chopper and of attending several weddings. She finally apologised to the Australian people for her behaviour on Thursday but is refusing to step down.

The Department of Finance is reviewing all of her expenses but Mr Abbott is standing by her.

It was reported on Saturday that one of her other charters – to Nowra on the NSW south coast – had cost taxpayers $6000. She attended several functions in the area, including Liberal fundraisers.

Mrs Bishop's office has refused to say whether the Nowra charter was arranged by the same political lobbyist, Andrew Gibbs, who was paid to organise the notorious chopper charter. Fairfax Media revealed last month that Mr Gibbs is best friends with Mrs Bishop's chief of staff, Damien Jones.

Opposition Leader Bill Shorten said these suggestions were "very serious".

"These reports take the seriousness of Bronwyn Bishop's misconduct to the next level," he said. "If Mrs Bishop's personal relationships influenced her decision to repeatedly hire a particular company, then that is incredibly serious."

Under current rules, speakers are allowed to take up to five overseas trips each year. The US trip would have been Mrs Bishop's third in 2015. She visited South America in January and Vietnam in March.

The US conference is convened by the Inter-Parliamentary Union, the organisation Mrs Bishop had hoped to lead. The 72-year-old unsuccessfully campaigned for its presidency last year, eventually losing out to a candidate from Bangladesh.

The vote came at the end of Mrs Bishop's lavish two-week European trip in which she racked up $88,084 in expenses: $25,400 on accommodation and food, $42,400 on airfares and almost $14,000 on private limos.

Mrs Bishop's fellow delegates spent a fraction of that amount.