Egyptian democracy activist Alaa Abdel Fattah has apologised for several of his old tweets that have resurfaced, as calls grow for him to be deported from the UK days after he arrived following his release from an Egyptian jail.

The Conservative and Reform UK leaders say the home secretary should consider whether Fattah, a dual national, can be removed from the UK, after social media messages emerged of him calling for Zionists and police to be killed.

The Times reports that some senior Labour MPs are also calling for Fattah’s citizenship to be removed.

After reviewing the historic tweets, Fattah said in a statement: “I do understand how shocking and hurtful they are, and for that I unequivocally apologise.”

He added, “I am shaken that, just as I am being reunited with my family for the first time in 12 years, several historic tweets of mine have been republished and used to question and attack my integrity and values, escalating to calls for the revocation of my citizenship.”

Fattah said he took allegations of antisemitism “very seriously” while arguing some of the posts had been “misunderstood, seemingly in bad faith”.

Sir Keir Starmer has been criticised for saying he was “delighted” by Fattah’s arrival in the UK this week, three months after he was freed from prison in Egypt, but it is understood he was unaware of the historical messages.

Conservative leader Kemi Badenoch and Reform UK leader Nigel Farage both said Home Secretary Shabana Mahmood should look at whether Fattah’s citizenship could be revoked to enable his swift removal from the UK.

Farage sais in a letter to Mahmood: “It should go without saying that anyone who possesses racist and anti-British views such as those of Mr el-Fattah should not be allowed into the UK,”

The Foreign Office said it had been “a long-standing priority under successive governments” to work for Abdel Fattah’s release and see him reunited with his family in the UK, but condemned his posts as “abhorrent”.

The 44-year-old was convicted in 2021 of “spreading fake news” in Egypt for sharing a Facebook post about torture in the country following a trial that human rights groups said was grossly unfair.

He was granted citizenship in December 2021 through his London-born mother – when the Conservatives were in power and Dame Priti Patel was home secretary.

The UK has responsibilities under international law to avoid leaving people stateless and British citizenship can only be stripped from someone eligible to apply for citizenship in another country.

Badenoch said Fattah’s reported comments were “disgusting and abhorrent” and anti-British, adding that citizenship decisions “must take account of social media activity, public statements, and patterns of belief”.

She said: “It is one thing to work for someone’s release from prison if they’ve been treated unfairly as previous governments did. It is quite another to elevate them, publicly and uncritically, into a moral hero.”

She added Fattah “should have received a free and fair trial in Egypt” but “there ends my sympathy”.

In his letter to the home secretary, Farage said it was “astonishing” that neither MPs from Labour, the Conservatives or other parties carried out “basic due diligence” on Fattah while they campaigned for Fattah’s release.

He said Sir Keir had showed an “extraordinary error of judgment” when he posted on X welcoming Fattah’s return.

Earlier shadow justice secretary Robert Jenrick said Fattah should “be made to live in Egypt or frankly anywhere else in the world”.

Jenrick said he did not consider it “defensible” that Fattah received British citizenship when his social media showed that he had “extremist views that are completely incompatible with British values”.

Fattah is also accused of saying the police do not have rights and “we should kill them all”.

The Board of Deputies of British Jews said the case was of “profound concern”.

Adrian Cohen, the board’s senior vice-president, said: “His previous extremist and violent rhetoric aimed at ‘Zionists’ and white people in general is threatening to British Jews and the wider public.

“The cross-party campaign for such a person, and the warm welcome issued by the government, demonstrate a broken system with an astonishing lack of due diligence by the authorities.”

A writer, intellectual and software developer, Fattah rose to prominence during an uprising in 2011 that forced the former Egyptian president, Hosni Mubarak, to resign.

He has spent more than a decade of his life behind bars and his release in September after a presidential pardon followed a long campaign by his family and lobbying by the British government.

In 2014, Fattah was nominated for a European human rights award, the Sakharov Prize, but this was withdrawn over tweets about Israel he posted in 2012.

He said those comments had been part of a “private conversation” that took place during an Israeli offensive in Gaza and had been taken out of context.

After being removed from a travel ban list imposed by Egyptian authorities that kept him in the country for three months after his release from jail, Fattah has now been reunited with his 14-year-old son, who lives in Brighton.