The U.S., not China, is seeking to change the status quo in the Taiwan Strait, the Chinese Embassy in London has said in a statement countering G7 claims.
A statement by G7 foreign ministers last week warned Beijing against seeking to "unilaterally change the status quo by force in the region."
The One China policy is at the heart of China's diplomatic relations with the rest of the world. It explicitly states that Taiwan and the Chinese mainland are an indivisible single country.
Beijing has therefore reacted angrily to a visit by U.S. House Speaker Nancy Pelosi to Taipei, the island's main city. It says the trip, which took place despite warnings, is part of continuing efforts to undermine the One China policy.
"We will not allow the US to continue to use salami tactics to encroach upon, obscure and hollow out the one-China principle. We will not allow the US to use any pretext or excuse to gradually change the status quo," the embassy said.
The embassy said China's response to the visit - including large scale military drills around the island - is "justified, reasonable and lawful."
"Our measures are firm, strong and proportionate," the statement continued. China says a reaction was required to ensure separatist forces did not threaten the peace and stability of the region.