Tory MPs have raised fears that the Standards and Privileges Committee investigation into whether Boris Johnson lied to Parliament over Partygate allegations during lockdown could be extended to the latest occupant of 10, Downing Street. Rishi Sunak was also fined along with the former Prime Minister for sharing a birthday cake in the Cabinet room.The concerns come as leading QC Baroness Heather Hallett this week prepares to decide the scope for the second half of the inquiry into the handling of the Covid pandemic.Baroness Hallett is expected to expand it to the conduct of Downing Street and Government departments during the two-year crisis and sources believe that both Mr Johnson and Mr Sunak could find themselves called in to receive a “grilling about Partygate”.The scandal, which ultimately forced Mr Johnson out of office, saw parties and heavy drinking going on in Downing Street when the rest of the country was in lockdown.Both Mr Sunak and Mr Johnson received a fine for a breach of their own rules for attending a birthday party ahead of an official meeting where the former Prime Minister’s wife Carrie shared cake.Mr Sunak always maintained that he was only guilty of turning up a few minutes early for a meeting on the pandemic where sandwiches were going to be shared anyway.However, some Tory MPs believe the fine makes him vulnerable now. Boris Johnson and Rishi Sunak were both fined over Partygate (Image: GETTY)One former minister told Express.co.uk: “The problem is that if you believe Boris Johnson lied to Parliament over Partygate – and I don’t as it happens – then you could make a case that Sunak did as well.”They both got fined, they both made statements saying they had done nothing wrong, so Sunak is as vulnerable as Boris.”There’s a real danger that Labour and the SNP will now push for the Standards and Privileges Committee investigation to look at what Sunak told Parliament as well.”That’s certainly what I would do if I was Labour.”Another former minister added: “Sunak is certainly not in the clear yet over this [Partygate].”READ MORE: Outrage as Truss to ramp up cost of Lords by handing out new gongs Baroness Heather Hallett is heading the covid inquiry (Image: PARLIAMENT)The Standards Committee in the Commons is being chaired by Harriet Harman, former Labour deputy leader because its chairman Chris Bryant declared that Mr Johnson was guilty before the inquiry began.But there are still fears that the committee’s inquiry is a “witch hunt” which has already predetermined Mr Johnson’s guilt over allegedly lying to Parliament.One Tory MP told Express.co.uk: “Boris didn’t lie intentionally and that’s the issue.”He opened his mouth and believed what he said in the moment it just happened not to be true.”DON’T MISSSunak abandons pledge to fine patients £10 for missed GP appointments [REVEAL]Sunak faces a nightmare on Downing Street warns DAVID MADDOX [INSIGHT]POLL – Should state pension rise under the triple lock [REACT] Harriet Harman is chairing the Standards Committee inquiry (Image: GETTY)Meanwhile, Baroness Hallett will announce this week whether Partygate will feature in the official covid inquiry as well.The covid inquiry was set up to learn lessons from the pandemic and its conduct.The first part of the inquiry will consider how well prepared the UK was for the disease which saw the country go into lockdown.But the second part of the inquiry will focus on government decisions and actions throughout the crisis.