Tulip Siddiq has been urged to stand aside from the anti-corruption aspects of her ministerial role by a group of anti-corruption charities.
Siddiq, whose role as Treasury economic secretary includes tackling corruption in UK financial markets, has been named in an investigation into claims her family embezzled up to £3.9bn from infrastructure spending in Bangladesh.
Conservative leader Kemi Badenoch called for the PM to sack his minister over the weekend.
The 42-year-old MP for Hampstead and Highgate has referred herself to the PM’s standards adviser and insists she has done nothing wrong.
The prime minister’s official spokesperson said on Monday afternoon that Sir Keir Starmer retained “full confidence” in his minister.
However, the UK Anti-Corruption Coalition, which includes organisations such as Oxfam and Transparency International, said Siddiq “currently has a serious conflict of interests”.
Siddiq has been named in an investigation by Bangladesh’s Anti-Corruption Commission (ACC) into her aunt, the country’s former prime minister Sheikh Hasina, who was deposed last year.
The investigation relates to a series of allegations made by Bobby Hajjaj, a senior political opponent of Hasina.
Court documents seen by the BBC show Hajjaj has accused Siddiq of helping to broker a deal with Russia in 2013 that overinflated the price of a new nuclear power plant in Bangladesh.
It is claimed that the deal inflated the price of the plant by £1bn, according to the documents – 30% of which was allegedly distributed to Siddiq and other family members via a complex network of banks and overseas companies.
The coalition of anti-corruption charities said there are “several urgent and important decisions for the international credibility and reputation of the UK” which the government needs to make that fall within Siddiq’s current brief, and “it is not clear that the minister is now in a position to take these decisions, given the conflict of interests that has arisen”.
The statement adds: “The Treasury minister is in charge of the UK’s framework on money laundering regulations and economic crime enforcement, while she also has direct family ties to a deposed regime that may be investigated under that framework.
“This conflict stands regardless of the outcome of the investigation by the independent advisor into whether a breach of the ministerial code has occurred.”
A Downing Street spokesman had earlier defended Siddiq, saying: “She’s acted entirely properly by referring herself to the independent adviser. That process is ongoing.”
Last week, Siddiq wrote to the prime minister’s standards adviser, Sir Laurie Magnus.
She said: “In recent weeks I have been the subject of media reporting, much of it inaccurate, about my financial affairs and my family’s links to the former government of Bangladesh.
“I am clear that I have done nothing wrong.
“However, for the avoidance of doubt, I would like you to independently establish the facts about these matters.”