HSBC is about to get away with cheating taxpayers of millions of pounds. HMRC, the agency responsible, is refusing to investigate. We're bringing a legal challenge to push them to act, but there is someone else that can take on these out-of-control bankers.

The Serious Fraud Office has the power to investigate and prosecute HSBC. We just need to get them to use it. If we can persuade the SFO to take on HSBC they could charge the bank themselves, with or without the tax authorities' help.

SFO Director David Green is an experienced criminal lawyer. He knows as well as we do that HSBC should be facing a criminal prosecution. Under his leadership the Serious Fraud Office has launched investigations against companies like Barclays and GlaxoSmithKline when there was a clear public interest. If enough of us report HSBC to the SFO, we can persuade him to investigate this bank too.

HSBC stands accused of aiding and abetting tax fraud on a global scale. Helping wealthy customers to hide their fortunes in secret Swiss accounts has deprived British taxpayers of millions of pounds. Bank executives even issued a public apology, admitting they had done wrong, but still no charges have been brought against them.

No company can be above the law, no matter how big or powerful. Last week, SumOfUs launched a ground-breaking legal action to force HMRC to investigate HSBC. We've hired a top lawyer who found there was a clear criminal case for HSBC to answer, and raised serious questions about tax authorities' judgement. If needs be we can use the courts to force HMRC to act, but if the SFO take on this case we won't have to.

The SFO have an email address anyone can use to report a fraud. They are actively seeking information from members of the public. So we should step up and complain about how HSBC has been behaving.