The Trump administration’s nominee to be the next US envoy to the United Nations has come under congressional scrutiny for absenteeism after spending more than half her time as ambassador to Canada away from her post.

Kelly Craft was asked why she spent more than 300 days outside Canada since she took the position in Ottawa in October 2017. In one two-month period between March and May in 2018, Craft was absent from her post 45 out of 54 days, according to Bob Menendez, the top Democrat on the Senate foreign relations committee.

“I find this staggering amount of time away from her post very troubling and an abdication of leadership,” he said.

Craft insisted that all her trips were taken according to state department regulations and argued much of the time was spent negotiating a trade deal with Canada and Mexico in Washington.

However, an investigation by Politico showed that a private jet registered to Craft’s husband, a US coal magnate, and used by the ambassador, made 128 flights between the US and Canada during a 15-month span of her tenure in Ottawa.

Seventy of those trips started or ended in Lexington, Kentucky, Craft’s home state. Some of those visits coincided with events there, including the Kentucky Derby and an interview at a basketball stadium named after her husband.

Menendez said that there were discrepancies in her account and suggested some of her social media posts suggested she was away from post at times not officially recorded. But he said that the committee could not make a judgment without a full report from the state department.

“The bottom line is, without the full record, we can’t evaluate it,” Menendez said.

The issue of Craft’s engagement in her job has arisen at a time when US-Canadian relations have been unusually tense, because of Donald Trump’s decision to walk away from an earlier North American trade agreement, Nafta, and his testy relationship with the Canadian prime minister, Justin Trudeau, who is due to visit Washington this week.

In her remarks to the Senate committee, Craft confirmed that she believed that human activity contributed to the planet’s climate emergency. She had previously called the science in question by saying she saw “both sides” of the argument.

On Wednesday, she told senators: “Climate change needs to be addressed as it poses real risk to our planet. Human behavior has contributed to the changing climate, let there be no doubt.”

However, she said the US should not bear an “outsized” share of the burden of the costs involved in reducing emissions, and that participation of the Paris climate accord was not necessary for the US to show “leadership”.