The son of a liberal Pakistani politician murdered for his moderate views has criticised Home Secretary Theresa May for allowing a radical Islamist cleric, who inspired the assasin, to enter the UK to preach.

Mufti Muhammad Hanif Qureshi spoke at a Luton mosque on Thursday May 4 as part of an event at the Jamia Islamia Ghousia Trust. A spokesman for the mosque confirmed Mufti Qureshi had made a "very, very impressive" speech to an audience of hundreds.

In 2011 politician Salmaan Taseer, who opposed Pakistan's anti-blasphemy laws, was shot dead by his bodyguard, Mumtaz Qadri. After his arrest, Qadri claimed he had been inspired to act by a 2010 sermon delivered by Mufti Qureshi in Rawalpindi, in which the cleric branded the likes of Taseer as liable to be killed under Islamic law.

Qureshi was arrested after Taseer's murder, but was not charged and subsequently released on bail. Qadri was sentenced to death for the murder, but in public sermons Qureshi continued to defend the assassin before he was hung in January 2016.

The home secretary can stop people entering the UK if she believes there is a threat to national security, public order or the safety of citizens.

Taseer's son, Shehryar, criticised UK authorities for allowing Qureshi to visit.

"He has in particular incited Mumtaz Qadri to murder my father. There is footage of that.

"What annoys me is how easy it is for him to manipulate the system, and I see him doing the same thing in going to the UK. He is not going there for a vacation, I am sure about that."

He said it was urgent the Home Office ban him travelling to Britain because of growing sectarianism in the UK "and growing trouble and violence in Europe as well. When someone gets a visa to the UK it is pretty easy to get visas to other big countries as well. These people should be confined. Why is this man allowed to travel abroad?"

A poster for an event at the Jamia Islamia Ghousia Trust in Luton on 4 May advertises Mufti Muhammad Hanif Qureshi "arriving exclusively from Pakistan" as a speaker.

The Luton mosque's senior cleric, Allama Qazi Abdul Aziz Chishti, defended the decision to invite Qureshi to speak, saying he has renounced his hardline views.

"Let me make it very clear to you that he has changed his views, and his speech was very, very impressive last night [4 May], and he made very clear that he believes that Islam is a religion of love and peace and harmony. Anyone who is killing innocent people is nothing to do with Islam," said Mr Chishti.

When asked whether the mosque backed the views Qureshi has expressed, Chishti said: "While we are living in this country we have got our own views. We are very clear we have got our own views and are living in accordance with the laws of this country."

Shehryar Taseer commented: "The rhetoric changes for the English-speaking media, and for Urdu speaking people it changes and becomes the opposite. It is easy for them [hardliners] to jump back and forth."

Qureshi is the founder of Shabab e-Islami, a religious organisation headquartered in Rawalpindi, which describes itself on its website as working "to promote peace, tolerance, interfaith harmony and education, tackle extremism and terrorism, engage with young Muslims for religious moderation, promote women's rights, development and empowerment".

Supporters of the group have held rallies in Pakistan in support of Qadri. Qureshi has been advertised as a speaker at the Luton mosque since 2014, with a number of recordings of sermons he delivered at the institution in Urdu available online.

Among the events he is advertised to speak at is the "36th annual" Khatme Nabuwwat meeting at the mosque. Branches of the Khatme Nubuwwat (Finality of the Prophet) movement have been implicated in the violent persecution of members of the Ahmadi religious sect in the UK and Pakistan.

In the Rawalpindi speech that inspired Qadri, Qureshi called on Sunni Muslims to kill those such as Taseer opposed to blasphemy laws.

"Let them know those who consider Sunnis as cowards that Allah has honoured us with the courage and power to strangulate those involved in blasphemy, to cut out their tongues, and to riddle their bodies with bullets. For this, nobody can arrest us under any law," said Qureshi in a recording of the sermon available on YouTube.

In March, Ahmadi shopkeeper Asad Shah was murdered in Glasgow, with his killer, Tanveer Ahmed, claiming he acted as Shah "disrespected" Islam. After the murder a Facebook page was set up, in which Ahmed was praised, alongside Qadri.

The Luton mosque is a registered charity, and in March Metropolitan Police Commissioner Sir Bernard Hogan-Howe visited to discuss "the fight against Daesh (Isis)" with Chishtli, according to a posting on the institution's website.

Rupert Sutton, an expert of domestic extremism at the Henry Jackson Society think tank, told IBTimes UK: "The fact is that [Qureshi] does have a clear record of inciting sectarian violence, which I think the Pakistanis have arrested him for in the past. Given the current climate following the murder of Asad Shah, it is very surprising there has not been more scrutiny of his invitation and of a registered charity inviting him to speak.

"The home secretary does have the power to exclude people entering the UK if there is a public safety issue, and in this case there does appear to be a public safety issue."

Spokesman Michael Charouneau said that the Home Office does not comment on individual cases.

"The Home Secretary has the power to exclude a foreign national if she believes their presence in the UK would not be conducive to the public good," he added.

IBTimes UK has attempted to reach Qureshi for comment.