Networks Grant Thronton International, RSM and Crowe Horwath International have all severed ties with their Iran member firms, following mounting pressure from US lobby group United Against Nuclear Iran (UANI) to exit the country.
UANI has previously lobbied successfully for the exit of the Big Four from Iran, leaving only mid-tier players in the market.
Grant Thornton International said in a statement it is no longer working with correspondant firm Rymand & Co.
"We want to reassure dynamic businesses in the Middle East that we will continue to work with them in helping unlock their potential for growth through our member firms in the region, and through our 35,000 Grant Thornton people working in more than 100 countries globally," Grant Thornton International said.
Last month UANI wrote to the network’s chairman Ed Nusbaum, saying: "The UANI believes that as the international community is working to economically isolate Iran in response to the regime’s illicit nuclear activities, the provision of accounting, auditing and other professional services by these accounting networks and associations is a boon to the Iranian economy and facilitates international commerce in Iran, often by creating a veneer of credibility and transparency that encourages foreign investment".
RSM also confirmed it had ceased the relationship with Dayarayan Auditing & Financial Services, which was the networks correspondent firm in Tehran, effective 30 April 2013.
"We have made this decision because of the increased level of sanctions on Iran and rising concern about the country’s political leadership. We agree with and support the work of UANI," RSM chief executive Jean Stephens said.
One of UANI main arguments is that international networks operating in Iran should not tender for US government contracts while profiting from their Iran operations. For many this is likely the biggest reason for withdrawal: for example KPMG, which was the last of the Big Four to leave the country in 2010, had US government contracts worth $1.2bn at the time, according to UANI.
UANI lobbies global accounting firm exit from Iran