The Labour chair, Anneliese Dodds, has written to her Conservative counterpart to seek assurances that all Tory leadership candidates will reveal if they have ever had non-dom tax status or used arrangements such as offshore holdings or stakes in shell companies. After revelations on Saturday about the chancellor, Nadhim Zahawi, the letter also requests information as to whether any of the would-be successors to Boris Johnson have been investigated over their financial affairs or had officials raise concerns about these. The fact that Sajid Javid and Rishi Sunak’s wife are already known to have used non-domiciled status for UK tax purposes could be “just the tip of the iceberg”, Dodds said. The letter was sent to Andrew Stephenson, the MP appointed in place of Oliver Dowden to co-chair the Conservative party, after it emerged that propriety and ethics officials noted a HM Revenue and Customs (HMRC) “flag” about Zahawi before his promotion from education secretary to chancellor. Zahawi, who has a personal fortune of more than £100m, has faced calls to explain the financial arrangements of his family trust, an offshore firm, Balshore Investments in Gibraltar. A source close to Zahawi said he “does not have, and never has had, an interest in Balshore Investments and he is not a beneficiary”. In the letter to Stephenson, Dodds said all Tory leadership candidates should say whether they or immediate relatives have benefited from non-dom tax status for overseas earnings and whether they support a Labour plan to remove the option. The letter also asks if they or their families possess offshore holdings, even through a shell company; whether they have funds in domestic shell companies or blind trusts; for details about any investigations into their affairs by HMRC, the National Crime Agency or the Serious Fraud Office; and whether Whitehall officials have ever raised concerns about their affairs. Dodds wrote: “Workers and businesses across our country pay their taxes and do the right thing. “It would further damage public trust in government if another Conservative prime minister enters No 10 under the impression that the rules which apply to everyone else do not apply to them.” In April, it emerged that Akshata Murty, the wife of Sunak, who resigned as chancellor last week, claimed non-dom status, allowing her to save millions of pounds in taxes on dividends collected from a stake in the tech company Infosys, founded by her father. It was then revealed that Sunak had held a US green card, giving him “permanent US resident” status for tax purposes for 19 months while he was chancellor and for six years as an MP. Javid then said he had held non-dom status for six years while a banker and held wealth in an offshore trust until he became a minister in 2012. The former foreign secretary Jeremy Hunt said on Sunday that he had never used non-dom status and that he would publish his tax details if required. Javid also said he would do so. Mr Hunt told the BBC’s Sunday Morning programme: “I’m very happy if I proceed to the final two, to publish my tax affairs, if that’s what other candidates do. But I’m not going to speak for other candidates. For myself, I would have no problem doing so.” When the Cabinet Office was asked about the “flag” raised over Zahawi, a spokesperson said: “Under the ministerial code, ministers must ensure that no conflict arises, or could reasonably be perceived to arise, between their ministerial position and their private interests, financial or otherwise. “The chancellor has followed the process set out in the ministerial code and complied with those requirements to the satisfaction of the previous independent advisers.” A spokesperson for Zahawi said: “All Mr Zahawi’s financial interests have been properly and transparently declared.” A source close to Zahawi said he and his wife had never claimed non-dom status.