Labour leader Sir Keir Starmer and his team have discussed whether he will promise to resign in the event of being fined by Durham police for breaking Covid rules.
The opposition leader is expected to make a statement at 16:00 BST.
Sir Keir has been under pressure after police announced they would be investigating an event at which he drank beer at an MP's office in 2021.
Labour has said Sir Keir was working, and insist no rules were broken.
But, Conservatives have accused Sir Keir of "rank double standards" as the opposition leader had previously called for Prime Minister Boris Johnson and Chancellor Rishi Sunak to resign over attending Downing Street lockdown events.
Durham police launched their inquiry on Friday after the local elections, having previously said they did not believe an offence had been committed.
The event under investigation took place at the constituency office of City of Durham Labour MP Mary Foy, where Sir Keir drank beer and ate curry, while lockdown restrictions were in place.
On Saturday, the Labour leader said he would take his party into the next general election, despite the police investigation.
However, speculation has since grown that he could pledge to step down if penalised by the police.
Senior Labour backbencher Dame Margaret Beckett told BBC Radio Derby she thought it "would be a very reckless thing to do" but added "it would not be untypical of Keir if that's what he thought he ought to do."
Sir Keir had been due to make a speech and take questions from journalists on Monday at an event organised by the Institute for Government (IoG) think tank, but he cancelled his appearance.
Labour's shadow health secretary Wes Streeting said his leader was not "ducking" questions adding that he was "a man of decency and honesty".
A Labour Party spokesperson said: "Keir was working. A takeaway was made available in the kitchen, and he ate between work demands. No rules were broken."
And Ms Foy dismissed allegations that some people who had been in her office were drunk as "untrue", adding: "I do not believe either I or my office staff broke any [Covid] rules."
Asked on Sky News whether Sir Keir should resign, Conservative MP and Universities Minister Michelle Donelan said: "This is a decision for him. He's going to have to search his soul after making this a top priority over the last few months at the expense of key issues like the rising cost of living.
"My takeaway is that it does smack of sheer hypocrisy," she added.
Keir Starmer discusses quitting if given Covid lockdown fine - BBC News