Labour shadow minister Kate Osamor has resigned from the party’s front bench, citing the “difficult time” her family is experiencing after her son was convicted of a drugs offence.

Jeremy Corbyn said he had accepted the shadow international development secretary’s resignation amid allegations the MP had threatened a journalist on her doorstep after being asked questions about her son’s conviction.

“I am resigning my position as shadow international development secretary to concentrate on supporting my family through the difficult time we have been experiencing,” Ms Osamor said in a statement on Saturday.

Her decision to step down comes after her son, Ishmael, who is also employed by the MP in her parliamentary office, pleaded guilty in September to four charges of possession with intent to supply after he was found with £2,500 worth of drugs at Bestival music festival last year.

Following the emergence of the case last month, Labour officials had claimed the shadow international development secretary was unaware of the incident until after Mr Osamor was given a community sentence of 200 hours of unpaid work in October.

But raising questions over the claims on Saturday, The Times reported the MP for Edmonton had known about the case before sentencing, as she had written to the judge asking for leniency.

And when approached by the newspaper outside her home in north London, the shadow cabinet minister allegedly threw a bucket of water at the journalist and said she “should have come down here with a bat and smashed your face in”. She was also reported to have called the police, after accusing the journalist of stalking her.

Ms Osamor’s office did not respond to these allegations when approached by The Independent, but she was condemned by the National Union of Journalists, who said: “Journalists, like any other workers, need to be able to go about their work without fear of threats or assault. It’s completely unacceptable to respond to legitimate press queries, however unwelcome they may be, with physical or verbal abuse.

“There is a disturbing and febrile international climate at the moment that is facilitating and legitimising the notion that it is open season on journalists – such insidious and dangerous beliefs, particularly when they emanate from public figures in positions of authority, have to be challenged at every turn.”

The Labour leader said: “I have accepted Kate Osamor’s resignation and would like to thank her for her work as our shadow secretary of state for international development. She brought a new dimension to the role by committing Labour to tackling global inequality as well as poverty as part of building a world for the many not the few.

“I know Kate will take this time to support her family, work for her constituents and support our party’s efforts to rebuild Britain from the back benches.”

The Labour MP Dan Carden has been appointed acting shadow international development secretary on a temporary basis, the party added.