A former Welsh Secretary has said Boris Johnson's apology for events held at Downing Street during lockdown "may not be sufficient".
Stephen Crabb, who was Welsh Secretary and Secretary of State for Work and Pensions, said the "reports of blatant breaches makes me feel extremely disappointed and genuinely let-down".
The letter has been shared by BBC journalist Lewis Goodall, who is tweeting letters from MPs to their constituents in response to the scandal.
"As you may be aware, there is an internal investigation currently underway by Sue Gray. I understand her report will be completed shortly and I look forward to seeing what it has to say. I know Sue well and have confidence in the work she is doing but her inquiries are limited to certain matters and may not be as conclusive as some might way.
"I note your comments regarding the Prime Minister's position. While he may not have attended some of the gatherings being reported, he does have a special responsibility in setting the culture and standards at the heart of government. He was right to apologise this week but this may not be a sufficient response given the seriousness of these matters."
There is no date yet for the publication of the Sue Gray report. When it was commissioned it was said to be needed to be completed "swiftly".
The Prime Minister will appear in front of the Commons today for Prime Minister's Questions from noon. You can follow that live with us here. There are reports today that backbench MPs are planning a coup. If 54, which is 15% of all MPs, submit no confidence letters to the chair of the 1922 Committee of MPs, a leadership challenge is triggered. The number of letters remains confidential and would only become public if the threshold was crossed.
There are reports a group of MPs elected in 2019 met on Tuesday to discuss their plans.
"I am acutely aware of the anger these revelations have generated and the pain they have caused. As I have explained to constituents previously, it was was incredibly difficult to vote in favour of some of the Covid rstrictions over the last two years knowing the impact they would have on families up and down the country. Seeing reports now of blatant breaches of these rules by some of those working within the Government I support makes me feel extremely disappointed and genuinely let-down.
"Please be assured that I have made the Prime Minister aware of the strength of feeling that exists in my own community about the events that have taken place at Downing Street. It is important that he is fully aware of the depth of public opinion on this emotive issue.
"I am discussing this further with my parliamentary colleagues and I will have more to say on this matter in due course.
"I appreciate your honest and frank opinion on this issue, and for taking the time to share this with me".
Mr Crabb previously put his name forward to be Prime Minister, a vote won by David Cameron. In 2016, he quit his role as work and pensions secretary "in the best interests of my family" after The Times reported that he sent sexually explicit WhatsApp messages to a young woman during the EU referendum campaign.
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