Former Alaska governor Sarah Palin has hit out at FBI director James Comey, claiming he has been 'tainted' by his ties with the Clinton Foundation.

Palin's comments, which she posted on her Facebook page, come as Comey announced the FBI's involvement in the investigation into Russia's alleged involvement in the US election.

"The swamp runs deep. Where are congressional 'investigators' on this conflict of interest issue?" Palin wrote on her Facebook page.

"Why aren't dots more clearly connected by those in authority, those privy to information that we peasants are not?

"Why is tainted Comey still part of Team Trump? How long does he get to ride the train?"

Comey also recently stated the Justice Department had found no evidence of wiretapping by former president Barack Obama of Donald Trump during the election campaign – something Trump had accused Obama of in a series of tweets.

On 4 March, Trump tweeted: "How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!

"I'd bet a good lawyer could make a great case out of the fact that President Obama was tapping my phones in October, just prior to Election."

Palin, who was once tipped to be considered for Donald Trump's cabinet but has since been critical of the president, also posted links on her Facebook page showing alleged links between Comey and The Clinton Foundation.

Palin endorsed Trump reasonably early on in the election process, and was at one point rumoured to be among those under consideration for the VP role, before it was given to Mike Pence.