Keir Starmer tonight said Suella Braverman must be fired after warnings her leak could have been hijacked for “insider trading”.
Labour wrote to “weak” Prime Minister Rishi Sunak demanding answers as Mr Starmer said: “He should sack her”.
Ms Braverman - nicknamed ‘leaky Sue’ - resigned after she broke the ministerial code by sending a draft document to two people outside government, including one by accident. Yet Rishi Sunak rehired her as Home Secretary six days later.
It’s understood the document involved a ‘growth visa’ plan to raise ‘high-skilled’ immigration.
A person familiar with such matters told the Mirror that, if it had fallen into the wrong hands, it could have enabled “de facto insider trading”.
This is because the scheme would have changed Office for Budget Responsibility forecasts on the deficit.
“You don't need to be a hedge fund to do that nowadays,” the person said. “It’s very easy to bet on Sterling movements from your phone.”
There is no suggestion the document was misused or passed on - and the person who received the e-mail by accident reported it.
But Shadow Chief Secretary to the Treasury Pat McFadden said: “We need urgent reassurances now that no market sensitive data was leaked.”
Keir Starmer said the “whole episode shows us just how weak the Prime Minister is”, adding: “He should sack her - that will be the strong thing to do. That's what I would do if I was prime minister."
Labour’s leader said: “We now know, it’s emerging, there’s also an economic risk in this.
“The danger here is that those around her won’t feel she’s the sort of person they can share classified information with.”
Rishi Sunak and Cabinet Secretary Simon Case were still resisting launching an inquiry.
But former head of the civil service Lord Kerslake warned Ms Braverman’s history was “a potential bomb” for the PM.
It emerged this week that MI5 were involved in a separate leak probe that looked at people including Ms Braverman in January.
An insider confirmed the separate probe to the Mirror, adding it went “all the way to the top”. However, it never found a culprit.
The Lib Dems demanded Ms Braverman surrender her texts, WhatsApps, and emails "for use in any future inquiry into her misconduct".
Home Affairs spokesman Alistair Carmichael said she “must be required to hand over all relevant evidence now before it is too late."
Rishi Sunak today refused to deny officials had warned him against rehiring Ms Braverman - but said he had no regrets.
He told reporters: “She's recognised she made a mistake, she's taken accountability for that and that's the right thing.
“She raised this topic with me when I discussed reappointing her as Home Secretary and I'm confident that she's learned from her mistake."
Ms Braverman previously insisted the document had been “due for publication imminently” and “much of it had already been briefed to MPs”.
Asked if the leaked document was a ‘growth visa’ plan, a No10 spokeswoman said: “I wouldn’t get into that kind of speculation”.
Asked about the link with the OBR, the spokeswoman replied: “I’m not getting into any speculation”.
