China has lambasted the United States, Britain and Japan for violating the one-China principle after the countries sent congratulatory messages to Taiwan's newly re-elected president, lauding the island's democratic system.

In a statement by the Foreign Ministry yesterday, spokesman Geng Shuang said Beijing has already made representations to these countries and urged them to keep their distance from the island.

Officials including US Secretary of State Mike Pompeo had sent congratulatory messages to Ms Tsai Ing-wen, lauding the island's democratic system, after she and her Democratic Progressive Party (DPP) won a landslide victory in Saturday's presidential election, and also held on to a parliamentary majority.

"We hope those countries will earnestly abide by the one-China principle, refrain from having any official ties or exchanges with the Taiwan region, deal with Taiwan-related issues properly and with caution, avoid sending any wrong signals to the 'Taiwan independence' forces, take concrete actions for the peaceful development of relations across the Taiwan Strait, and uphold the larger picture of their own bilateral relations with China," said Mr Geng.

The US recognises Beijing as the sole legal government of China under its one-China policy, as does the United Kingdom and Japan.

A separate statement earlier by China's Taiwan Affairs Office also reiterated Beijing's commitment to unify Taiwan with the mainland under its "one country, two systems" model, and warned that China would "resolutely safeguard national sovereignty and territorial integrity, resolutely oppose separatist attempts and acts for 'Taiwan independence' in any form".

In a landslide victory seen as a rebuke of China and its bid for unification, Ms Tsai claimed 57 per cent of the total votes while her rival, the China-friendly Han Kuo-yu of the Kuomintang, drew just 39 per cent.

Chinese state media was quick to accuse the newly re-elected Taiwanese President of using "dirty tactics" to win her second term in office, saying she and her party had resorted to "cheating, repression and intimidation to obtain votes".

Official Chinese news agency Xinhua described Ms Tsai and the DPP's purported underhanded tactics as having "exposed their selfish, greedy and evil nature".

"Anti-China political forces in the West openly intervened in Taiwan's elections and supported Tsai in order to contain the Chinese mainland and to prevent the two sides of the Taiwan Strait from getting closer," it said.

The nationalistic Global Times tabloid also accused Ms Tsai and her team of having "exploited administrative resources and crushed their opponents through approaches devoid of a bottom line".

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It cited the island's anti-infiltration law, hastily pushed last month through Parliament, where the DPP has a majority, to counter China's political influence ahead of the presidential vote.

"The level of the pro-secession camp's demonisation of the mainland has reached a peak in recent years. Their description of the Chinese mainland and its Taiwan policy cannot be more absurd," said the op-ed.

Relations between China and Taiwan, which Beijing considers a part of the mainland, have deteriorated since Ms Tsai first took office in 2016. After she rejected the 1992 Consensus, an agreement that there is just one China, Beijing cut off official dialogue and sought to pressure Taiwan by poaching its diplomatic allies, ramping up military exercises and banning individual tourist travel to the island.

Experts say Beijing is hoping Ms Tsai will back down from her hardened rhetoric formed around protecting Taiwan's sovereignty and rejecting the "one country, two systems" model.

While Ms Tsai has said she is not about to change the status quo with China, her party largely favours formal independence, the biggest red line for China.

Dr Hoo Tiang Boon, who researches cross-strait relations at the S. Rajaratnam School of International Studies, said analysts have theorised that as China faces growing pressure from the US and would not want the Taiwan issue to be hijacked by Washington, it may rethink its strategy in dealing with Ms Tsai's government.

"It would seem to make sense for China to lower its own bar and communicate with the DPP regime, but I'm not so optimistic," said Dr Hoo.

In a speech after her win, Ms Tsai reiterated her willingness for cross-strait dialogue but stressed Taiwan will "never concede to threats".