The prime minister's special representative on internet safety has said that MPs should not be sharing their work computer passwords with staff.
Baroness Shields's advice follows an admission by three Conservative MPs that they had given their login details to their assistants.
There have also been suggestions that the practice is relatively commonplace.
Sharing passwords is not a breach of the UK's Data Protection Act.
But House of Commons staff are explicitly banned from disclosing their own passwords. And documents posted online by the Associated Press news agency indicate MPs are advised to act likewise.
"Never share your password or write it down where others could find it," states one guide written for MPs.
"We can arrange for your staff to access your mailbox, calendar and documents through their own accounts."
Baroness Shields – who served as Minister for Internet Safety and Security before adopting her current role – told the BBC that she did not plan to make a formal intervention.
But she suggested that MPs should reconsider out-of-date practices.
"I don't think anybody should be sharing their passwords," she said.
"It used to be that you could share passwords, there wasn't this constant threat.
"But the way cyber-threats have evolved is that we need to anticipate the next threat.
"There is always someone trying to get in – trying to view emails or understand what's going on, and you have to assume that you are always under threat."
The matter came to prominence over the weekend, when Nadine Dorries – MP for Mid Bedfordshire – tweeted that a "frequent shout" in her office was "What is the password?"
She had made the point to cast doubt over claims that First Secretary of State Damian Green must have been responsible for viewing pornography allegedly found on his computer.
But the intervention meant that she and two other MPs that have since acknowledged password-sharing – Will Quince and Peter Grant – have become embroiled in controversy themselves.
The Information Commissioner's Office has said it is also looking into the matter.