Ministers have been accused of a “totally inadequate” response towards Chinese diplomats who violently confronted pro-democracy protesters in Manchester. The foreign secretary, James Cleverly, said he had summoned a senior Chinese diplomat over the “completely unacceptable” incident outside the consulate on Sunday. However, senior Tories complained that this reprimand was not delivered by a minister but by a Foreign Office official “who simply rapped them over the knuckles”. Sir Iain Duncan Smith, the former Conservative party leader, said this was “totally inadequate” and said ministers should tell the Chinese diplomats that “if they do not follow our rules, they get expelled”. The Commons Speaker, Sir Lindsay Hoyle, said ministers could be required to address the concerns in the Commons, adding that “we were all appalled by those images and quite rightly action needs to be taken”. A pro-democracy Hong Kong protester, Bob Chan, needed overnight hospital treatment after being beaten by men who appeared to emerge from the consulate to confront campaigners over “offensive” banners. Chan said on Wednesday he was “shocked and hurt by this unprovoked attack”. He added: “I am shocked because I never thought something like this could have happened in the UK.” One of China’s most senior diplomats in the UK, Zheng Xiyuan, claimed in a letter seen by the Guardian that his staff were attacked by a mob who had “stormed” the Manchester consulate. Footage posted online showed a person believed to be Zheng, the consul general, kicking down banners and forcefully grabbing Bob’s hair before the protester was pulled inside the consulate grounds and beaten. The UK government has been urged to prosecute or expel any Chinese officials found by Greater Manchester police (GMP) to have attacked campaigners. Footage filmed by campaigners appeared to show several men, including one wearing a riot helmet and two wearing stab vests, emerge from the consulate and start tearing down banners before the violence erupted. Several of these men were filmed punching and kicking Chan after dragging him inside the grounds of the consulate, where UK police need permission to enter. A police officer could then be seen pulling Chan away from the assailants, the footage showed. In a letter to police, given to the Guardian and Manchester Evening News, the consul general claimed that Chan had “plunged” into the property after grabbing a member of consular staff by the neck. Zheng said the activists had displayed slogans that were “deliberately designed to provoke, harass, alarm and distress our consular staff” and as a result were contrary to the Public Order Act. He said the activists were “asked politely” to remove the imagery “but refused to do so”. Zheng claimed that the banners included a picture of China’s president, Xi Jinping, with a noose around his neck, along with slogans in Chinese saying “God kill CPC” and “fuck your mother”. He said he was “disappointed” that the police “did not do more to ensure that the protesters exercised their right in a respectful rather than aggressive manner”. Zheng added in the letter: “At one point the consulate grounds were stormed by a group of protesters and members of consular staff were required to physically fend off unauthorised entry and subsequent assaults. “During the ensuing scuffle, one of the protesters grabbed a member of consular staff by the neck and refused to let go. In an effort to free the staff member, other members of staff pulled their colleague into our compound. Despite this, the attacker persistently refused to let go and plunged into the property himself.” Greater Manchester police has taken statements from some of those involved in the incident, including Chinese officials who cannot be prosecuted due to diplomatic immunity. The force is due to pass its findings to the UK Foreign Office, which will then decide what action is appropriate. Any expulsion of Chinese diplomats would be met with fury from Beijing. The assistant chief constable Rob Potts said: “We’re aware and totally understand the amount of focus on this investigation due to the weekend’s events causing shock and concern in the city and much wider afield.”