The Metropolitan Police are investigating allegations Chinese embassy guards brandished illegal electroshock batons at protesters.
The government has also been urged to take action after the alleged incident.
Videos appeared to show security staff at both the current Chinese embassy in Portland Place and the proposed new embassy at Royal Mint Court, near the Tower of London, wielding the weapons in two separate incidents in recent months, the i Paper have reported.
Electroshock weapons are banned in the UK.
The Met said officers are reviewing evidence, “including video footage supplied by witnesses”.
Downing Street officials said the matter has been raised with the embassy directly and warned that foreign diplomats must abide by British laws.
The Chinese embassy described the claims about its security staff at Portland Place as “nothing but fabrication and defamation” by “Tibetan independence elements” who “attempted to force their way into the embassy premises”.
The Prime Minister’s official spokesperson said he would not “get ahead” of the police investigation but added: “If there’s evidence a crime has been committed, we won’t hesitate to act.
“Any attempts by a foreign state to coerce, intimidate, harass or harm individuals on UK soil will never be tolerated.
“We expect all foreign diplomats in the UK to abide by our laws, in the same way we expect all UK diplomats to do so when posted overseas, and we’ve raised this incident directly with the Chinese embassy.”
Shadow national security minister Alicia Kearns urged the government to take more action, describing the police investigation as a “dead end” that was unlikely to result in prosecution because of international protections for embassy premises.
She said: “Nine weeks after the incident, with evidence of prohibited electroshock weapons on more than one Chinese site, the Government has done nothing but ‘raise’ the incident with the embassy.
“The Chinese Communist Party has broken British law, and potentially the Vienna Convention, and yet rather than respond to the threatening of peaceful vigil holders with illegal weapons, ministers are hiding behind a dead-end Met investigation they know won’t end with prosecutions.
“If the Government won’t act when laws are broken, and people are threatened on British soil, it is inviting the Chinese Communist Party to test them again.
“The Government needs to deter future threats, but that requires them to act, now.”
A Met Police spokesperson said: “On Friday 3 July at around 1800hrs, police were called to reports of a protest outside the Chinese Embassy on Portland Place, W1B.
“Officers attended the scene. Two protesters alleged that embassy staff had pointed a Taser towards them. No injuries were reported and officers left the area once the protesters had dispersed on their own accord.
“No arrests have been made at this stage. The investigation continues as officers review evidence, including video footage supplied by witnesses.”
The Met urged anyone with information to call police on 101, quoting CAD7335/03JUL26.
