The chair of an influential Westminster sleaze watchdog has warned that it is no longer sufficiently ethnically diverse, after the appointment of a Bullingdon Club friend of Boris Johnson left an all-white governing panel.

In a highly unusual letter to cabinet minister Michael Gove, Lord Evans of Weardale warned of a lack of “visible diversity” among members of the Committee on Standards in Public Life and said the watchdog “needs to be representative of the people we serve”.

The departure of Monisha Shah and the appointments of Ewen Fergusson and Professor Gillian Peele in July left the eight-strong committee all-white for the first time since at least 2015.

In his letter, former MI5 boss Lord Evans said that a number of members of the committee had “expressed concerns about our lack of visible diversity now as a group”.

He warned Mr Gove: “With a remit across public life, the committee needs to be representative of the people we serve.”

And he urged the Cabinet Office minister to ensure the department gives “due weight” to the issue of maintaining diversity when filling the next expected vacancy in January next year.

The appointment of City solicitor Mr Fergusson sparked controversy last month because he was a member with the prime minister of Oxford University’s exclusive male-only Bullingdon Club dining society.

He appeared alongside Mr Johnson and David Cameron in the famous 1987 photograph of club members posing in its uniform of white tie and tails.

Former committee chair Sir Alistair Graham denounced Mr Fergusson’s appointment at the time as “completely inappropriate”.

And he today told The Independent that it was vital the committee - which advises the prime minister on arrangements for upholding ethical standards of conduct across public life in England - should be representative of the nation’s people.

“There’s been a lot of serious question marks over appointments made during the pandemic,” said Sir Alistair. “I think it is unfortunate that this feeling has developed that you have got to have gone to the same school or university or be good mates with a senior minister to be appointed to public.

“It is true to say that all public institutions, and certainly the CSPL, should have a representative mix of people from the population as a whole, including people from ethnic minority groups.

“Members from ethnic minority backgrounds might bring a different perspective to standards issues and they might be more fully aware of what is affecting participation in politics by those communities. It is about making sure that there is a full integrity of the committee by being genuinely representative.”

Mr Fergusson and Prof Peele were on a shortlist of qualified candidates to replace Ms Shah and Jane Ramsey drawn up by a panel including Lord Evans and an independent member alongside two Cabinet Office officials, but the final choice was made by Mr Gove.