Producer Daisy Ayliffe was working with Channel 4 reporter Alex Thomson, who was trying to question mother-of-one Tulip Siddiq about a British barrister detained in Bangladesh .
After a heated confrontation with Mr Thomson, the Hampstead and Kilburn MP, whose aunt is Prime Minister of Bangladesh, snapped at Ms Ayliffe: “Hope you have a great birth because child labour is hard.”
Channel 4 has complained to the Labour party about her “apparently threatening” remark.
In a tweet yesterday, Ms Ayliffe said: “The perils of being a pregnant journalist: An MP might use it against you.”
Justine Roberts, chief executive of parents’ website Mumsnet, said: “Giving birth is a hard experience for many women… raising the issue at the end of a bruising professional encounter seems both odd and unkind.”
The row broke out over Ahmad bin Qasem, a barrister who trained in Britain and is said by human rights groups to have been abducted by Bangladeshi security forces.
Channel 4 approached Ms Siddiq, 35, at the weekend during a rally in support of British mother Nazanin Zaghari-Ratcliffe, who has been imprisoned in Iran, to ask about Mr Qasem’s plight.
The MP, an outspoken campaigner for her constituent Mrs Zaghari-Ratcliffe, told the TV crew: “Be very careful.
“I’m not Bangladeshi and the person you are talking about, I have no idea about their case. That is the end of my statement.”
Ms Siddiq, who sits on the Parliamentary Women and Equalities Committee, then walked away.
She told the producer: “Thanks, Daisy, for coming. Hope you have a great birth because child labour is hard.”
The London-born MP, who lived in Bangladesh between the ages of five and 10, has made a complaint to police over the confrontation, alleging assault by a cameraman.
Yesterday she said: “I want to apologise unreservedly for my comments to Channel 4’s producer, which were an offhand and ill-judged attempt to deal with what I felt was a hostile situation.
“I would never want to upset her and I hope she accepts my apology.”