The UK Foreign Office accused Home Secretary Theresa May of hampering efforts to reopen the British Embassy in Tehran and undermining "delicate negotiations" for normalization of ties with Iran.
According to a report by the Telegraph on Tuesday, Theresa May is said to be delaying progress by refusing to reopen a visa office at the embassy – a key demand by Tehran – until 4,000 Iranians are deported from Britain.
They include asylum seekers and residents whose visas expired during the three year suspension of diplomatic ties after an attack on the British Embassy in Tehran.
"The Home Office refuses to open a visa service while undocumented Iranians remain in Britain. It's definitely holding things up," the Telegraph quoted one Foreign Office official as saying.
The Times quoting senior government sources also reported that Mrs. May could undermine delicate negotiations to rebuild relations with Iran.
The two sides have been discussing "technicalities" of the issue since last year after June when then foreign office secretary William Hague announced plans for the embassy to be reopened.
In November 2011, Britain cut its ties with Tehran and withdrew its diplomatic staff from Iran and ordered the staff of the Iranian Embassy in London to leave the country.
The move came after an angry group stormed the British Embassy in Tehran to protest Britain's policy on Iran. Parliament had earlier voted in favor of downgrading diplomatic relations with Britain.
Nearly two years later in October 2013, and following the election of President Hassan Rouhani, the two countries agreed to appoint non-resident chargés d’affaires as a first step toward restoration of ties.
A British government source also said there was "a lot of frustration" within the department over May's interference.
Richard Bacon, a Conservative MP who recently became chairman of the parliamentary group on Iran, described the delays as "very frustrating", the Telegraph reported.
Bacon also said further delays in reopening embassy "is damaging the outlook of relations with Iran."
Foreign Minister Mohammad Javad Zarif said on Wednesday, "Tehran has decided to move toward normalizing ties between the two states and reopening embassies; however, political issues aside there are technical and administrative processes that need to be addressed," ISNA reported.
"We are ready to treat the British Embassy in Tehran like other embassies and expect the UK to do the same with respect to our embassy in London," Zarif stressed.