Mr Hancock this week announced he had been appointed a special representative to the UN in an unpaid role.
The former cabinet minister, who resigned in June after admitting he broke coronavirus restrictions during relations with an aide, said he would be helping African countries to recover from Covid-19.
But according to Pass Blue, an independent organisation covering the UN, the offer will not be taken up by the organisation.
The media group quoted UN spokesman Stephane Dujarric saying: “Mr Hancock’s appointment by the UN Economic Commission for Africa is not being taken forward.
“ECA has advised him of the matter.”
The BBC said it also understood that the position would no longer be offered to Mr Hancock.
Reacting to the reports, Nick Dearden, director of campaign group Global Justice Now, said: “It is right for the UN to reconsider this appointment.
“If Matt Hancock wants to help African countries recover from the pandemic, he should lobby the Prime Minister to back a patent waiver on Covid-19 vaccines.
“If he’d done that when he was in government, tens of millions more people could already have been vaccinated across the continent.
“The last thing the African continent needs is a failed British politician.
“This isn’t the 19th century.”
The original announcement was criticised as it came on the same day a damning report from MPs was published on how errors and delays by the Government and scientific advisers cost lives during the pandemic.
In a letter posted on Twitter by Mr Hancock on Tuesday, the under secretary-general of the UN, Vera Songwe had originally said that the West Suffolk MP’s “success” in handling the UK’s pandemic response was a testament to the strengths he will bring to the role.
After making the initial announcement on social media, Mr Hancock was congratulated by a host of ministers, including Foreign Secretary Liz Truss and Culture Secretary Nadine Dorries.
Mr Hancock’s time in the Cabinet was cut short four months ago after leaked CCTV footage showed him kissing an aide, in breach of social distancing rules that he had helped establish as health secretary.
Mr Hancock has been approached for comment.