Dame Andrea stopped short of calling for a leadership challenge but warned it is up to individual Tories to ‘decide what is the right course of action’.
The former business secretary stopped short of calling for the Prime Minister’s resignation or a leadership contest in her statement to South Northants constituents today (Tuesday).
But she warned: “Each of my Conservative MP colleagues and I must now decide individually on what is the right course of action that will restore confidence in our government.”
The PM received one of 126 fines over breaching lockdown rules in Downing Street.
After carefully studying Sue Gray’s report, Dame Andrea said: "it is painfully clear to me that, given the extent and severity of rule-breaking taking place over a 20-month period, it is extremely unlikely that senior leaders were unaware of what was going on."
“I therefore, agree with Sue Gray's conclusions that there have been significant failures of leadership, both political and official, in No 10 and the Cabinet Office.
“The conclusion I have drawn from the Sue Gray report is that there have been unacceptable failings of leadership that cannot be tolerated."
The report set out details of 15 events where officials spilled red wine on walls of No 10, vomited, got into a fight, used a karaoke machine and continued festivities until 4am while the country was subject to strict curbs on socialising.
In a series of statements, the PM said he had attended “work events” to boost morale.
Dame Andrea said it was clear the PM was personally shocked by the reports findings, adding: “It was right that he humbly apologised to the nation and to all those who lost loved ones.
"He also apologised to support staff who were treated disrespectfully by certain staff, whose behaviour was particularly abhorrent and unacceptable.
“I note that the thorough investigation by the Metropolitan Police concluded that rule breaking by the prime minister personally was limited to a surprise birthday party organised for him. This confirms the prime minister’s statement that he was not personally involved in any lockdown breaches.
“I believe in the importance of high standards of integrity, and that Members of Parliament must strive to be good role models, very specifically because we are the lawmakers and therefore in a trusted position of power and authority.
"I am determined to be clear about my views as a matter of personal integrity. The conclusion I have drawn is there have been unacceptable failings of leadership that cannot be tolerated and are the responsibility of the prime minister.”
Daventry’s Chris Heaton-Harris, who was promoted to chief whip in December, tweeted: “There are many issues our country faces and Parliament needs to look outwards and address those. Our PM is a man who has consistently got the big calls right and will continue to do so.”
Andrea Leadsom pulled out of the race to be leader of the Tory party in 2016.