Iran has sentenced an Iranian national to 10 years in prison for spying for Britain.

“An Iranian who was in charge of the Iran desk in the British Council and was cooperating with Britain’s intelligence agency … was sentenced to 10 years in prison after clear confessions,” Gholamhossein Esmaili, a judiciary spokesman, said on state television.

He did not identify the person who was sentenced but Aras Amiri, a 33-year-old London-based British Council employee, was arrested last year during a family visit to Iran. Her case has similarities to that of Nazanin Zaghari-Ratcliffe, the Iranian-British dual national arrested three years ago allegedly for spying and now in jail for more than two years.

Amiri was visiting her home country to see her ailing grandmother before the Persian new year, in March last year, when she was detained, said her cousin, Mohsen Omrani.

Amiri’s detention was part of a string of arrests involving British dual nationals or Iranians linked with British institutions.

Omrani said Amiri had been accused of colluding and acting against the national security of Iran. At the time Omrani said Amiri had visited Iran frequently in the past without any issues. “She never had any problems before,” he said. “She went to Iran this time for a brief visit to see her grandmother who is in hospital in [the city of] Amol.”

The British Council said Amiri had not been on a work assignment during her visit to Iran. A spokesperson said the council was aware that “one of our staff has been detained in Iran while making a private family visit. The colleague is an Iranian national.”

The British Council is Britain’s cultural agency overseas and it no longer has offices or representatives in Iran. It works remotely to develop cultural links with Iran, but is struggling to develop a strategy to rebuild trust between the countries.

Iran has a history of hostility towards the British Council, which is a UK charity governed by royal charter and a UK public body, receiving a 15% core funding grant from the UK government.

In 2009, Iran closed the British Council offices in Tehran in reaction to the launch, in London, of the BBC’s Persian service, which is detested by the Iranian establishment. In June 2009, following unrest in the aftermath of a disputed presidential election, Iran arrested several local staff working for the British embassy in Tehran.

The council’s chief executive, Sir Ciarán Devane, said: “We have seen reports that an Iranian national, claimed to be an employee of the British Council, has been sentenced.

“However, we have not been able to confirm that this is our colleague. Our colleague’s safety and wellbeing remain our first concern, as it has been throughout their detention. We are in close contact with the Foreign and Commonwealth Office.”

The British Council said a colleague who was detained last year was not head of “the Iran desk” but instead worked in the UK in a junior role to support and showcase the Iranian contemporary art scene to UK audiences. The British Council does not have offices or representatives in Iran and does not do any work in Iran.

Devane said: “The British Council is the UK’s international organisation for cultural relations and educational opportunities, working in arts and culture, English language, education and civil society. We are a non-political organisation committed to people-to-people engagement, and our staff are not connected to any espionage agency. We believe that when political or diplomatic relations become difficult, cultural exchange helps to maintain open dialogue between people and institutions.”

A spokesman for the UK Foreign Office said: “We are very concerned by reports that an Iranian British Council employee has been sentenced to jail on charges of espionage. We have not been able to confirm any further details at this stage and are urgently seeking further information.”