SYDNEY (Reuters) - China summoned Australia’s ambassador to lodge a complaint last week over Canberra’s allegation that Beijing had sought to interfere in Australian politics, a source familiar with the diplomatic action told Reuters on Thursday.

Relations between Australia and China became strained in recent weeks after Canberra said it would ban foreign political donations as part of a crackdown aimed at preventing external influence in domestic politics, sharpening the focus on China’s soft power.

Australian Prime Minister Malcolm Turnbull singled out China as he said foreign powers were making “unprecedented and increasingly sophisticated attempts to influence the political process” in Australia.

In response, China summoned Ambassador Jan Adams to a meeting at the Chinese Ministry for Foreign Affairs on December 8 to lodge a complaint, the source said.

Chinese Foreign Ministry spokesman Lu Kang confirmed the ministry had an “important discussion” with the Australian ambassador.

“The Australian side should be very clear about China’s position on the relevant issue,” Lu told a daily news briefing, without elaborating.

China’s Foreign Ministry said last week Turnbull’s allegations were full of prejudice against China, were baseless and poisoned the atmosphere of China-Australia relations.

Turnbull’s allegations have been criticized by Australia’s opposition Labor Party as showing an “anti-China” bias that could jeopardize bilateral trade.

China, which is easily Australia’s biggest trading partner, bought A$93 billion ($70 billion) worth of Australian goods and services last year. Australia’s unshakeable security relationship with the United States, however, has limited how cosy it gets with China.

Turnbull denied indulging in anti-Chinese rhetoric, insisting Labour was using the issue to win favor with a large voter block ahead of a make-or-break by-election on Saturday that analysts said will determine his political future.

“I am disappointed they have tried to turn Australians against each other,” Turnbull told reporters in Sydney.