Donald Trump’s campaign directed Republican party operatives named as “alternate” electors in Georgia to operate with “complete secrecy and discretion” as the then president attempted to overturn his defeat by Joe Biden.

The startling direction was contained in an email which is part of a US justice department investigation, CNN and the Washington Post reported.

Trump lost to Biden by more than 7m ballots in the popular vote and by 302-236 in the electoral college – the same margin Trump called a landslide when it was in his favour over Hillary Clinton (who won the popular vote by nearly 3 million) in 2016.

Pursuing the lie that Biden’s win was the result of fraud, the Trump campaign sought to overturn its electoral college defeat in part by appointing its own electors in seven key states.

On 13 December 2020, a Georgia campaign official, Robert Sinners, emailed alternate electors due to gather the next day.

He wrote: “I must ask for your complete discretion in this process. Your duties are imperative to ensure the end result – a win in Georgia for President Trump – but will be hampered unless we have complete secrecy and discretion.”

The alternate electors were to gather at the statehouse in Atlanta.

Sinners told them: “Please, at no point should you mention anything to do with presidential electors or speak to media.”

The meeting did not take place in secret as local media filmed it.

A lawyer for the chairman of the Georgia Republican party, David Shafer, told the Post and CNN: “None of these communications, nor his testimony, suggest that Mr Shafer requested or wished for confidentiality surrounding the provisional electors.

“Quite to the contrary, Chairman Shafer invited TV news cameras into the proceedings and both issued a statement and gave a televised news interview immediately afterward.”

At the time, Schafer said the meeting was necessary in case Trump won any legal challenges in key states.

But Trump failed in his attempt to hold on to power, whether through slates of alternate electors, court challenges or the deadly attack on the US Capitol by his supporters on 6 January 2021, an attempt to stop certification of electoral college results.

Speaking to the Post, Norm Eisen, a former ethics tsar under Barack Obama, counsel to House Democrats in Trump’s first impeachment and now a senior fellow at the Brookings Institution, said of the email to Georgia alternate electors: “If there was nothing wrong with it, why go through such extraordinary lengths to hide what you’re doing?”

Sinners told CNN and the Post he worked at Shafer’s direction, and “was advised by attorneys that [secrecy] was necessary in order to preserve the pending legal challenge”.

He added: “Following the former president’s refusal to accept the results of the election and allow a peaceful transition of power, my views on this matter have changed significantly from where they were on 13 December” 2020.

Sinners now works for Brad Raffensperger, the Republican secretary of state who resisted Trump’s demand he “find” enough votes to overturn Biden’s win in Georgia – a win recounts confirmed.

Trump’s call to Raffensperger is under criminal investigation in Georgia. The district attorney in question is also investigating the alternate electors scheme. So is the House January 6 committee, which will hold public hearings this week.

In the federal investigation, Jason Shepherd, a former chairman of the Republican party in Cobb county, Georgia, told the Post he had been interviewed by the FBI.

“They seem the most interested in Shafer’s role and any communications from the White House or members of Congress,” he said.

Trump advisers under scrutiny include Rudy Giuliani, the former mayor of New York who became Trump’s personal attorney.

Patrick Gartland, a would-be alternate elector who ultimately did not take part in the scheme, told the Post he too had been questioned by FBI agents.

“They wanted to know if I had talked to Giuliani,” he said.