The British government has deliberately delayed taking steps necessary to secure the release of Nazanin Zaghari-Ratcliffe – including payment of a £400m debt owed to Iran – for fear of offending the Trump administration, lawyers acting for the British-Iranian woman have alleged. The lawyers requested a meeting with the defence secretary, Ben Wallace, and his advisers at the “earliest convenience” to discuss the approach the government was taking on the issue of debt owed to Iran. In a seven-page letter to Wallace, the lawyers accuse the government of procrastination and claim the UK’s approach to securing the release of dual nationals from Tehran jails has been far less effective than those of other countries – including the US. A BBC Panorama programme broadcast a similar charge on Monday night. Zaghari-Ratcliffe has been under effective house arrest in Tehran since March when she was given temporary release from prison having served four years of a five-year sentence for alleged espionage. She was arrested in Tehran in April 2016. Her husband, Richard Ratcliffe, has alleged that her full release has been held back by the UK’s failure to settle an acknowledged £400m debt over an arms deal with the late shah of Iran. In the letter to Wallace, the lawyers say it is astonishing that International Military Services (IMS), a UK government agency, “continues to raise every possible legal objection to payment of the debt and has plainly failed to engage in constructive dialogue with Tehran”. The letter claims the Foreign Office evades and prevaricates when it is asked the simplest questions on the steps it may be taking to pay the debt, which has been the subject of more than a decade of court disputes. It says a decision to defer the next high court hearing on the debt until 4 November, a day after the US presidential election “in effect plays politics with the lives of British citizens”. The lawyers claim: “The UK government is apparently waiting for implicit permission from the US government to pay the UK’s legally owed debts, payment of which would allow Nazanin (and other innocent British nationals) finally to come home. The message appears to be that the safety of British citizens abroad is subordinate to falling in line with US policy.” The UK stance is somewhat paradoxical, the letter says, in that the US has itself negotiated two prisoner swaps with Iran recently. It also claims British tactics have failed to deter the Tehran regime, saying: “There has been a new wave of forced confessions and prisoners being tortured, a new programme of family members of activists and prisoners being arrested, more instances of second sentences being levelled against cellmates of Nazanin who would otherwise be eligible for release.” Part of the purpose of the letter is to warn the UK government that its actions risk endangering the freedom of more British dual nationals. The letter concludes: “It is important that the UK both honours its legally owed obligations to Iran, but also calls out the Iranian government on its illegal treatment of Nazanin under Iranian law. However, the UK government has done precisely the opposite: obtusely refusing to discharge its legal obligations, whilst remaining silent and appeasing Iran in the face of Tehran’s atrocious abuse of Nazanin’s human rights.” The letter was sent to Wallace as the Ministry of Defence is a 99% shareholder in IMS. As a backbencher, Wallace objected to the UK’s non-payment of the debt. But the letter claims Wallace as defence secretary has “become party to the waiting game that you so vigorously opposed: a deliberate policy of procrastination and delay, coupled with the fallacious insistence that the roadblocks to repayment are unavoidable”. The Ministry of Defence said: “The defence secretary’s position on this matter has not changed. As previous government statements have made clear, we remain committed to securing the immediate and permanent release of all arbitrarily detained dual British nationals in Iran and regularly lobby for their release at the highest levels. This includes through the prime minister, the foreign secretary and the British ambassador in Tehran.”