Rebekah Brooks and her racehorse trainer husband are among six suspects arrested today by detectives investigating phone hacking at News International.

The former News International chief executive and Charlie Brooks were arrested at their Oxfordshire home on suspicion of conspiracy to pervert the course of justice, sources said.

Police are searching several addresses after dawn raids also took place in London, Hampshire and Hertfordshire, Scotland Yard said.

Ms Brooks, a former editor of The Sun, had been on bail after being questioned by detectives last summer on suspicion of phone hacking and corruption.

Today's arrest come after her lawyer, Stephen Parkinson, said evidence given by Sue Akers at the Leveson Inquiry had brought "much prejudicial material" into the public domain.

Mrs Brooks, 43, is being questioned at an Oxfordshire police station while Mr Brooks is being interviewed at a Buckinghamshire police station.

The racehorse trainer, who writes for the Daily Telegraph, described in his column yesterday the pubs he would visit as part of his outing to the Cheltenham Festival.

The arrests come after it emerged that Scotland Yard agreed to lend Mrs Brooks a horse for two years, prompting fresh scrutiny over relations between police chiefs and News International.

Mrs Brooks was first arrested and questioned last July, days after resigning as chief executive.

Officers from Operation Weeting - the inquiry into voicemail interceptions - said they consulted the Crown Prosecution Service before carrying out the operation.

Officers said the four other men - aged 39, 46, 38 and 48 - were arrested in raids in Hampshire, west London, Hertfordshire and east London.

A Scotland Yard statement said: "The co-ordinated arrests were made between approximately 5am and 7am this morning by officers from Operation Weeting, the MPS inquiry into the phone hacking of voicemail boxes.

"All six - five men and one woman - were arrested on suspicion of conspiracy to pervert the course of justice, contrary to the Criminal Law Act 1977.

"A number of addresses connected to the arrests are being searched. Today's operation follows consultation with the Crown Prosecution Service."

A total of 22 people have now been arrested under Weeting, which has been running since January last year, Scotland Yard said.

The Scotland Yard Deputy Assistant Commissioner, who is leading the investigation into illegal newsgathering, has told the inquiry into press standards that there was a "culture of illegal payments" at the Sun newspaper.

Ms Akers, who is in charge of three linked inquiries into phone hacking, illicit payments and computer hacking, told Lord Justice Leveson the payments appeared to have been authorised at a "senior level".

This week it was announced that the Attorney General is looking into concerns the policewoman could have prejudiced any potential trials.

Mrs Brooks, who resigned last year as News International chief executive amid the furore over phone-hacking allegations, "fostered" Raisa the horse after it retired from active service in 2008.

She paid food and vet bills until Raisa was rehoused with a police officer in 2010, months before fresh investigations began into illegal activities at the News of the World.

Mrs Brooks is the only suspect being questioned who had already been arrested under Weeting, a source said.

The arrest is potentially embarrassing for David Cameron, who earlier this month was forced to make further admissions about the extent of his relationship with Mr and Mrs Brooks.

After it emerged that Scotland Yard had lent an ex-police horse, Raisa, to Mrs Brooks, the Prime Minister conceded the animal had been among his mounts on rides with Mr Brooks - a friend from their Eton schooldays.

Asked whether the horse riding was emblematic of those overly close ties, Mr Cameron said: "I have known Charlie Brooks, the husband of Rebekah Brooks, for over 30 years.

"He is a good friend and he is a neighbour in the constituency. We live a few miles apart."

Asked about the arrest. a Downing Street spokeswoman said: "The Prime Minister is travelling to Washington. It is an operational matter for the police. You wouldn't expect him to comment on it."

Mark Hanna, director of group security at News International, is also among the six suspects, a spokeswoman for the company said.