Prime Minister Boris Johnson, along with Chancellor Rishi Sunak, was slapped with a fine by the Metropolitan Police last week over Covid lockdown breaches in Downing Street.
But as the fines were issued in recess, today is one of the first genuine opportunities for Sir Keir Starmer to put the PM on the spot.
Labour will today put forward its motion seeking to refer Mr Johnson for investigation by the Privileges Committee to determine whether he misled Parliament.
Sir Keir will hope to capitalise on the political leverage this offers, as the Committee has wide-ranging powers and could ask to look at the Sue Gray report.
It also has the power to recommend sanctions.
Boris Johnson apologised for Partygate in the Commons yesterday
UK Parliament/Jessica Taylor
Sir Keir called the apology a 'joke'
UK Parliament/Jessica Taylor
But the chances of Labour’s motion being successful are slim as Sir Keir faces a “very tall order” to get enough Tory MPs to vote for an investigation, according to The Telegraph’s Ben Riley-Smith.
He added: “Thursday’s vote may be more about how many Tories abstain than vote for it.”
The political capital could still be huge even if the motion fails, though.
Sir Keir will hope to use it as ammunition against Tory MPs at the local elections in May, and the next general election – likely to be held in 2024.
A Labour source told Politico: “Any Conservative MP considering voting to block this investigation would be voting for a cover-up.
“They should reflect on the mess they got themselves into over Owen Paterson before falling into line.”
Mr Johnson appeared in the Commons yesterday, where he said sorry after the Met Police fines.
But Sir Keir called the apology a “joke” and Tory MP Mark Harper broke ranks from his colleagues by calling on the PM to resign over his “indefensible” actions.
The Labour leader went on to bring up the story of John Robinson, whose wife died of Covid.
Sir Keir said John "followed the Prime Minister's rules" and didn't visit his wife in hospital in an address that visibly moved the Tory benches.
But speaking to GB News' Tom Harwood, Tory MP Michael Fabricant hit out at Sir Keir and other Labour MPs for "choosing to weaponise the personal tragedies endured by people".