Constance Briscoe, a friend of Vicky Pryce, was arrested after telling police she had not been in contact with the media about the story, when it later appeared that she had, Pryce's retrial heard today.
Pryce, 60, denies perverting the course of justice, claiming Huhne coerced her into taking three points for him in 2003.
Last week a jury failed to reach a verdict in Pryce's trial, prompting a retrial at Southwark Crown Court which started yesterday.
The court has heard Pryce, helped by Briscoe, told journalists about the story to get revenge on Huhne after he left her for PR adviser Carina Trimingham in June 2010.
Prosecutor Andrew Edis QC today read jurors a statement from Detective Inspector Martin Passmore explaining why certain people had not been called as witnesses in the case.
"Ms Briscoe has provided statements to the police in this case but during the investigation it became apparent that she may have lied about her involvement with the press and that she denied having any contact with the Mail on Sunday or any other media organisation in relation to this story," his statement said.
"Ms Pryce has not been arrested or interviewed in relation to that allegation.
"For this reason Ms Briscoe has been arrested and is currently under investigation by the police.
"Ms Briscoe could therefore no longer be relied upon as a witness of truth and on October 2, 2012 the Crown Prosecution Service took the decision not to call Ms Briscoe to give evidence in the case."
Yesterday Mr Edis told the court Ms Briscoe was a friend and neighbour of Pryce.
"She was a neighbour of Vicky Pryce in those days and I think she had also had a difficulty in her marriage and they appear to have got closer to each other," he said.
"The two of them appear to have cooked up a plan to go and see the press about Huhne and taking points.
"They started it together by approaching a man called Andrew Alderson."
Mr Alderson was a freelance journalist working to provide the story to the Mail on Sunday, the court heard.
Mr Edis said Pryce and Ms Briscoe told Mr Alderson that Huhne had passed speeding points to constituency aide Jo White.
"Vicky Pryce and Constance Briscoe went to see Alderson and the story they were giving him was it was Jo White who worked for Huhne in his constituency in Eastleigh," he said.
"The story they were giving the papers was Jo White took points for Huhne when he had nine points.
"Well, of course, that was a complete lie because the person who took points for Huhne when he had nine points was her (Pryce)."
The jury was told about emails between Ms Briscoe and Mr Alderson, and Mail on Sunday news editor David Dillon.
One email from Ms Briscoe to Mr Dillon on November 30 2010 explained that the "relevant person" had been "bullied and pressurised" into taking Huhne's points.
It said: "Finally, you will appreciate that I have no particular interest in this story save that I have been asked to act as an intermediary on behalf of the relevant person."
Sunday Times political editor Isabel Oakeshott - who published the story in May 2011 after Pryce confessed to her in March that year - yesterday told the court that although she knew the Mail on Sunday was aware of the story, Pryce had not told her that Ms Briscoe was acting as an intermediary for her with the rival paper.
She said she was not aware the barrister had any dealings with the Mail on Sunday, but knew she was a close friend of Pryce.
In his statement, Det Insp Passmore said neither Mr Alderson nor Mr Dillon would be called as witnesses in Pryce's trial.
"Mr Dillon and Mr Alderson have both declined to provide a statement in this case," he said, adding that their "journalistic material" was protected by law.
"As far as I am aware there is no basis in law for the police to compel Mr Dillon and Mr Alderson to provide a statement or to enter court to give evidence in this case."
Former energy minister Chris Huhne pleaded guilty to perverting the course of justice and resigned as MP for Eastleigh at the start of the first trial and will be sentenced once this trial is over.
The court heard yesterday that Mr Alderson sent Ms Briscoe an email on December 10, asking: "Do we have lift off - ie a statement to the MoS?
"If so, I suspect he will be an ex minister by Sunday lunch-time ..."