The home secretary, Priti Patel, is to take on the security minister’s responsibilities permanently after James Brokenshire left the portfolio last month, according to reports.

Brokenshire announced his resignation on 7 July, telling Boris Johnson that his recovery from lung cancer treatment was “taking longer than anticipated” after a resurgence of the illness he was diagnosed with two years ago.

Patel will take over his brief on a permanent basis after covering the role for more than a month, the Times reported.

The move came shortly after Labour claimed that the arrest on Tuesday of a British man in Berlin on suspicion of spying for Russia raised “questions” about the prime minister’s failure to fill the security post. The shadow security minister, Conor McGinn, said it “beggared belief” that the role had not been filled five weeks on.

The Metropolitan police commissioner, Dame Cressida Dick, said on Thursday that her force had been involved in the Berlin case for “a number of months”.

A Home Office spokesperson said on Wednesday: “The home secretary is responsible for all areas of Home Office business, including those related to national security.”

The security minister brief outlined on the government’s website is extensive. Responsibilities include counter-terrorism, serious and organised crime, cybercrime, economic crime, hostile state activity, extradition, and royal and VIP protection.

It also covers online harms; the common travel area between the UK, Ireland, the Isle of Man and the Channel Islands; aviation and maritime security; Grenfell; and flooding, hurricane, and natural disaster relief.

During the Covid-19 pandemic, the minister also oversaw the functioning of the domestic national security system, including MI5, counter-terrorism policing, as well as the functioning of the serious and organised crime system, including the National Crime Agency, and cybersecurity.