BORIS Johnson’s former anti-corruption tsar has warned the Prime Minister would be making a “big mistake” if he refuses to appoint a new ethics adviser.

Tory MP John Penrose said that if Mr Johnson left the post vacant following Lord Geidt’s resignation on Wednesday it would leave “really quite damaging questions dangling”.

After being pushed to the brink over Mr Johnson’s conduct over the Partygate scandal, Lord Geidt quit after saying the PM had put him in an “impossible and odious” position.

He accused Mr Johnson of risking a “deliberate and purposeful breach” of his own ministerial code by potentially breaking World Trade Organisation rules over Chinese steel tariffs.

Lord Geidt was the second ethics adviser to quit during Mr Johnson's premiership over disagreements with him.

Despite Downing Street admitting that advisers on the ministerial code performed a “vitally important” function, it also said the PM was now reviewing the post and could abolish it.

Mr Penrose, a former minister, told BBC Radio 4 this morning: “I think that would be potentially quite a big mistake.”

“I think one of the reasons why it’s important to have some continuity, why it’s important to have, if not a precise replacement, then an effective succession here, is to make sure that you don’t leave really quite damaging questions dangling and that anything that’s outstanding doesn’t just get forgotten and lost.

He added: “I just think that the Prime Minister is currently overdrawn, if I can put it that way, on his account with both the voters and with the parliamentary party. 

“They need to show that they’re serious about this.”

Mr Penrose quit his anti-corruption role last week in order to vote against Mr Johnson in the confidence vote of MPs, accusing him of breaking the ministerial code over Partygate.

Labour demanded a direct replacement for Lord Geidt after he became the second man to resign from the role during Mr Johnson’s premiership.

However Tory business minister Paul Scully said he would be comfortable without a replacement ethics adviser as long as ministers are held to account in another way.

He told Sky News: “I think I would be comfortable with that as long as there is a mechanism that (ensures) the Prime Minister and that me as minister are held to the highest standards.

“There is a ministerial code there and we want to make sure that it’s adhered to, because it (enshrines) the principles that we all stand on, not just as MPs when we first come into the House, but when we accept office as ministers.”

The FDA union representing civil servants warned that the code is the only way workers can raises complaints of misconduct, bullying or sexual harassment against ministers.

But No 10 said Mr Johnson will “carefully consider” how best to fulfil the role of ensuring “rigorous oversight and scrutiny of ministerial interests”.

“We haven’t made a final decision on how best to carry out that function, whether it relates to a specific individual or not,” the Prime Minister’s official spokesman said.

In 2020, Sir Alex Allan was the first of Mr Johnson’s ethics advisers to resign after the Prime Minister refused to accept his finding that Home Secretary Priti Patel bullied civil servants.

Sir Alex backed Lord Geidt’s resignation as principled, arguing that the trade policy disagreement was the tipping point after a series of scandals including Mr Johnson being fined by police for breaking coronavirus laws.

He told BBC Newscast on Thursday: “I think this was the final straw coming on top of, for example, his concerns about the fact the Prime Minister hadn’t said anything about the Ministerial Code in all of his explanations of the partygate saga”.