Lord Evans, chair of the Committee on Standards in Public Life, gave a damning assessment of Boris Johnson's government's approach to standards and ethics as it faces another allegation of having a party at Number 10 while the country was locked down in 2020.

The former MI5 chief told MPs: "We have seen a whole series of issues over the last few months: the Owen Paterson affair, the attempt to change the rules over standards investigations in the middle of the investigation into Mr Paterson's actions, the questions around the redecoration of Downing Street and particularly the very bad processes that were clearly in place for keeping Lord Geidt properly informed, the Greensill affair and now 'partygate'.

"All of those I think have demonstrated that there is at least a carelessness amongst people in government over standards issues, and possibly more than that."

He said media reports and polling over the past few months show "people are concerned about these issues".

"People care and feel that those people who are representing them in parliament, those people who are being paid to undertake public roles should be living up to the standards that they profess to live up to," he added.

Hours before Lord Evans' appearance in front of the Commons Public Administration and Constitutional Affairs Committee, a senior Conservative told Sky News claims Mr Johnson and his wife Carrie attended a drinks event at No 10 in May 2020 were "indefensible".

Less than an hour before the alleged garden party happened, the public was told from a room in Number 10 that they must adhere to the strict lockdown rules, which included a ban on outdoor group gatherings.

A Whitehall investigation into multiple allegations of coronavirus rule-breaking in both Number 10 and other government buildings has now been widened to include two alleged events on 15 and 20 May 2020.

Lord Evans also told the committee all methods of communication - including WhatsApp messages - regarding official business should be covered under disclosure requirements when being investigated.

Last week, the PM's independent standards' adviser Lord Geidt told of his "grave concern" about not being made aware of WhatsApp messages between Mr Johnson and a Tory donor while investigating how the PM's Downing Street flat was funded.

The PM had said he only discovered who had funded the refurb in February 2021, but the WhatsApp messages revealed Lord Brownlow accepting his request for more money for the flat in November 2020.

Lord Evans hit out at the use of WhatsApp by ministers, telling the committee: "There is a responsibility on anybody who is conducting public business to be able to give an account of that.

"In principle, it doesn't seem like a very good idea for substantive public business to be being transacted on WhatsApp but you have to live in the real world and it probably is.

"I personally felt there may be other technical solutions that are better than WhatsApp for this purpose but that's beyond my remit.

"It is absolutely clear the responsibility is if you are conducting public business then there needs to be public accountability for that, irrespective of which channel you choose.

"There may be compliance challenges and people need to look at that and think about whether you say 'you're not to use WhatsApp you're to use something else which can be more regulated'."