The timing could hardly be worse for Downing Street. With Labour facing mounting criticism over its domestic agenda and the Prime Minister's approval ratings declining, a protracted privileges committee investigation would dominate Parliamentary business and distract from the government's legislative programme. Conservative MPs are likely to seize the opportunity to portray Labour as embodying the same culture of evasion they campaigned against during the previous administration.

Tuesday's vote will test whether the Prime Minister can rely on his substantial Parliamentary majority to defeat the motion. Labour backbenchers will face a difficult choice: support their leader and risk accusations of hypocrisy given Labour's previous demands for Johnson to be investigated, or vote for an investigation that could damage their own government. The outcome will send a clear signal about whether Westminster's mechanisms for holding power to account apply equally regardless of party—or whether they remain tools of partisan warfare.

For political observers who have covered Westminster for two decades, this moment represents a familiar pattern. Governments arrive promising transparency and accountability, then face their first real test when those principles collide with political survival. The question is not whether Starmer technically misled Parliament—that will be for the committee to determine if an investigation proceeds—but whether Parliament itself still commands sufficient authority to demand answers from a Prime Minister with a commanding majority.

As Tuesday's debate approaches, Downing Street will be working frantically to shore up support and frame the allegations as politically motivated. But precedent, once established, becomes difficult to ignore. Johnson's referral to the privileges committee began with similar claims of partisan attacks, yet ended with cross-party agreement on his misconduct. Whether Starmer faces the same trajectory remains to be seen, but Westminster's memory is long, and its appetite for consistency—when it chooses to exercise it—can be unforgiving.