The US secretary of state, Mike Pompeo, has renewed his attack on HSBC for the bank’s alleged treatment of pro-democracy customers in Hong Kong, saying that China is “bullying” the UK.

Pompeo, who in June accused HSBC of a “corporate kowtow” to Beijing, cited reports of Hong Kong-based executives at Next Media being unable to access their bank accounts. He accused the bank, which is based on London but makes most of its profits in Hong Kong and China, of “maintaining accounts for individuals who have been sanctioned for denying freedom for Hongkongers while shutting accounts for those seeking freedom”.

“Free nations must ensure that corporate interests are not suborned by the CCP [Chinese Communist party] to aid its political repression,” Pompeo said on Wednesday. “We stand ready to help the British government and its companies resist CCP bullying and stand for freedom.”

HSBC, which is struggling to balance its need to stay in favour with China while the US and Britain remain critical of Beijing’s handling of Hong Kong’s pro-democracy movement, declined to comment.

The bank has also come in for criticism from Aviva Investors, one of Britain’s biggest investors and a top 20 shareholder, after Peter Wong, HSBC’s Asia-Pacific chief executive, signed a petition that backed China’s plans to enact a sweeping security law in Hong Kong.

Last month, the UK foreign secretary, Dominic Raab, reprimanded HSBC and other banks for supporting the controversial security law, saying the rights of the people of Hong Kong should not be sacrificed for bankers’ bonuses.

HSBC’s chief executive and his counterpart at Standard Chartered – which is also London-based but also one of Hong Kong’s biggest banks – have already been censured in a letter from Labour frontbenchers. The shadow chancellor, Anneliese Dodds, and the shadow foreign secretary, Lisa Nandy, urged both CEOs to withdraw their support for legislation.

The members of the shadow cabinet warned the banks in a letter that they could face a boycott and urged them to uphold Britain’s democratic values.

The US has criticised Beijing’s crackdown against pro-democracy opposition in Hong Kong after the security law was imposed on 30 June. The move by Beijing has also been widely condemned by other western nations.

The Hong Kong media tycoon Jimmy Lai, a prominent pro-democracy activist and top executive at Next Digital, was arrested this month under the law, further stoking concerns about media and other freedoms promised to Hong Kong when it returned to China in 1997.