Canada said Friday "past incidents and behaviours" are to blame for China's official news agency and the Communist Party newspaper being banned from an Arctic trip with Prime Minister Stephen Harper.

Jason MacDonald, the top Harper spokesman, said in an email from the North that "some media outlets are not welcome on the trip" when asked if reporters for the People's Daily and the Xinhua News Agency had been banned.

The decision follows Li Xuejiang of the People's Daily having pushed former Harper spokeswoman Julie Vaux during last year's trip to the Arctic after she prevented him from asking a question. 

In a telephone interview, Li acknowledged pushing Vaux but said the prime minister's office discriminated against Chinese journalists by not allowing him to ask a question.

"For racial reasons?" he said. "They didn't give me any reason."

Li, the bureau chief for the Communist Party newspaper and a former Washington correspondent, said he couldn't understand why he was silenced and later manhandled by police. Harper's staff limits the number of questions at public events. 

Li said he didn't even apply to go on this year's trip. 

Xinhua News Agency reporter Baodong Li said he applied but was told he could not go because of a lack of space. He doesn't understand why he was banned.

"This is really ridiculous. This is not just against Mr. Li of the People's Daily, it's also against all the Chinese journalists," Baodong said. "It has nothing to do with me."  

Li and Baodong said they are considering issuing a complaint with the Ottawa press gallery. 

David Mulroney, Canada's ambassador to China from 2009 to 2012, said journalists in China can be quite aggressive, and have been for some time. 

"I was once in a melee as they stampeded into a meeting room to get a photo of then-president Jiang Zemin. I believe that journalism is one of those critical aspects of Chinese society that is changing slowly but steadily," Mulroney said in an email. 

The ban comes at a time of strained relations between Canada and China. The Canadian government recently accused Chinese hackers of infiltrating the computer systems of Canada's top research and development organization. China denied it. Just a few days later Chinese authorities arrested a Canadian couple in China on suspicion of stealing state secrets about military and national defense research. They remain detained.