The lawyers trying to remove Hamas from the UK’s list of proscribed terrorist groups should be investigated and potentially struck off, Robert Jenrick has demanded.

The Conservative shadow justice secretary has called for “a thorough and transparent investigation” of Riverway Law by the Solicitors Regulation Authority (SRA).

In a letter to the watchdog, Mr Jenrick said there is “a clear need to uphold public confidence in the legal profession and to ensure rigorous enforcement of the UK sanctions regime”.

On Thursday, the firm made a legal application to Yvette Cooper, the Home Secretary, challenging the proscription of Hamas in the UK as a terrorist organisation.

In their 106-page application, Riverway argued the proscription should be lifted in line with European Convention of Human Rights (ECHR) protections for freedom of speech. It claims the ban is disproportionate and that Hamas poses “no threat to the UK people”.

The appeal, believed to be the first of its kind, is being fronted by Mousa Abu Marzouk, Hamas’s head of international relations and its legal office.

Mr Jenrick wrote that there are “significant questions as to whether Riverway have complied with their obligations under the UK sanctions regime, the SRA’s own published guidance, and broader professional standards expected of solicitors”.