The backlash against Donald Trump if he fired special counsel Robert Mueller would be “like nothing you’ve seen”, a former US government ethics chief has warned the president.

“America is stronger than you,” Walter Shaub told the Republican who last night plugged a Fox News programme featuring strong criticism of Mr Mueller and deputy attorney general Rod Rosenstein, following the raid on his personal lawyer’s office.

Mr Shaub, who served as director of the US Office of Government Ethics from 2013 to 2017, tweeted: “Dear @realDonaldTrump, stop and reflect on how things got worse for you after firing Comey.

“If you go after Mueller or Rosenstein, the reaction will be like nothing you’ve seen.

“America is stronger than you because our forefathers were smarter than you and they planned for you.”

Mr Trump fired FBI director James Comey last May over what were described as “serious mistakes” in his handling of the investigation into Hillary Clinton’s use of a private email server.

It came after a meeting between the pair in which Mr Trump was said to have asked the director for his “loyalty”, and a public declaration that he was not personally under investigation over Russian election meddling.

But Republican congressman Mark Meadows, a Trump ally, said he did not expect a new purge.

“The president is not talking about firing Mueller. I’ve had conversations with the president, and he’s not talking about it,” Mr Meadows said.

On Monday the FBI raided the offices of Michael Cohen, a long-time Trump associate, in what the president described as a break-in and “disgraceful situation”.

A search warrant used in the raid sought bank records, business records on his dealing in the taxi industry and Mr Cohen’s communications with the Trump campaign, according to people familiar with the investigation.

Agents further seized records on a $130,000 (£92,000) payment to adult actress Stormy Daniels, who claims she had sex with Mr Trump. The president has said he was not aware of the payment.

The raid was overseen by the US Attorney’s office in Manhattan and was based in part on a referral from Mr Mueller.

Mr Mueller is investigating alleged collusion between the Trump campaign and Russia. Mr Trump has described the probe as a “witch hunt” and on Wednesday said it was “fake and corrupt”, headed by “Democrat loyalists, or people that worked for Obama”.

He tweeted: “Mueller is most conflicted of all (except Rosenstein who signed FISA & Comey letter). No Collusion, so they go crazy!”

Additional reporting by agencies