The government is facing calls to carry out an urgent investigation after reports emerged that a phone belonging to Liz Truss was hacked by Russia.
The Liberal Democrats and the Labour Party have described the allegations as "extremely serious" and "concerning".
Agents suspected of working for Russian President Vladimir Putin allegedly hacked the former prime minister's personal phone during the summer Tory leadership campaign, gaining access to details of negotiations with key international allies.
Private messages between the then foreign secretary and cabinet minister Kwasi Kwarteng were also accessed, according to the Mail on Sunday.
These details were reportedly suppressed by Boris Johnson, who was prime minister at the time, and Cabinet Secretary Simon Case.
The government has not confirmed the reports and Sky News has not been able to independently verify the claims.
Speaking to Sky's Sophy Ridge on Sunday, Secretary of State for Levelling Up Michael Gove insisted the government takes security issues "incredibly seriously".
He said: "I don't know the full details of what security breach, if any, took place.
"What I do know is that the government has very robust protocols in place in order to make sure that individuals are protected, but also that government security and national security are protected as well.
"I think all of us have to be sensitive, particularly those of us in government, to the fact that the more we talk in detail about these things, the more that we risk giving information to people who wish this country and its citizens harm."
Speaking to Sky News, chair of the Defence Select Committee Tobias Ellwood said he was not aware of the incident but had seen the reports.
"This is a constant threat from Russia, they are getting better and better at these cyber attacks and hacking. We take the most stringent measures to make sure it doesn't happen," he told Sky News.
"It is something for the intelligence and security committee to investigate further."
'Serious questions' need to be answered
In response to the report, shadow home secretary Yvette Cooper said the "serious allegations" raise "serious questions about why this information or this story has been leaked or briefed right now".
Speaking to Sophy Ridge on Sunday, she said: "I really hope that this hasn't been leaked, for example, to try and distract from some of the other things that are happening, because obviously I think actually it does the opposite and just raises wider concerns about the way in which the government is not taking seriously enough these issues around national security."
She added that the person who should be "providing reassurance that the government has a grip" is Suella Braverman, but "she can't do that because she's still unable to answer those serious questions about her own security breaches and lapses".
'Unforgivable' if information was withheld to protect Truss
Meanwhile, the Liberal Democrats called for an urgent investigation to take place and said the allegations raise "serious questions" for Mr Johnson.
The party's foreign affairs spokesperson Layla Moran asked: "Was Liz Truss's phone hacked by Russia, was there a news blackout and if so why?
"If it turns out this information was withheld from the public to protect Liz Truss's leadership bid, that would be unforgivable.
"We cannot allow the Conservative Party's political games to be put ahead of the country's interests and national security," she added.
A government spokesperson said there are "robust systems" in place to protect against cyber threats, including regular security briefings for ministers and advice on how they can protect their personal data.
But, they added: "We do not comment on individuals' security arrangements."