Donald Trump’s ousted national security adviser has established a fund to raise money to meet the “tremendous” legal costs he faces as a result of him being investigating by special prosecutor Robert Mueller.

Former general Michael Flynn was in February forced to resign from Mr Trump’s team after it emerged he had misled people about his contacts with Russian officials. It has since emerged that both he and his son have become a focus of Mr Mueller’s probe into possible collusion between the Trump campaign and Russia’s alleged attempt to interfere with the 2016 election.

It has also been reported that Mr Flynn’s son, Michael G Flynn, has become a target for investigators as a result of his work for his father’s lobbying firm.

Mr Flynn’s relatives are behind the online legal defence fund, which asks “veterans, and all people of goodwill” to contribute. The fund was established by Mr Flynn’s brother, Joe, and sister Barbara Redgate.

“The costs of legal representation associated with responding to the multiple investigations that have arisen in the wake of the 2016 election place a great burden on Mike and his family,” they said in a statement.

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“They are deeply grateful for considering a donation to help pay expenses relating to his legal representation.”

Mr Flynn, who has been quiet on social media for at least a month, posted a statement from him and his wife, to thank his siblings for their input.

Michael Flynn once said anyone seeking immunity 'probably committed a crime'

“Lori and I are very grateful to my brother Joe and sister Barbara for creating a fund to help pay my legal defense costs,” he said.

Mr Flynn was fired by Mr Trump as national security adviser after less than a month on the job. The ousting came 18 days after a senior Justice Department official warned that Mr Flynn could be blackmailed because Moscow knew he made misleading statements about his contacts with Russian officials, including Russia’s Ambassador to Washington, Sergey Kislyak.

Reuters said that in August, Mr Flynn reported income of at least $1.8m, according to an amended financial disclosure form, which included paid speaking engagements to Russian entities, including the Kremlin-funded RT TV and Volga-Dnepr Airlines and payments for lobbying for the Turkish government.