Donald Trump offered WikiLeaks founder Julian Assange a pardon if he said Russia was not involved in the leak of Democratic National Committee emails, a court has heard.

The claim emerged as Assange, 48, appeared at Westminster Magistrates’ Court ahead of an extradition hearing next week.

His barrister Edward Fitzgerald QC highlighted evidence alleging former US Republican Congressman Dana Rohrabacher had been to see Assange, while he was still in the Ecuadorian embassy in August 2017.

He said a statement from Assange’s lawyer Jennifer Robinson shows “Mr Rohrabacher going to see Mr Assange and saying, on instructions from the president, he was offering a pardon or some other way out, if Mr Assange… said Russia had nothing to do with the DNC leaks”.

A series of emails embarrassing for the Democrats and the Hillary Clinton presidential campaign were hacked before being published by WikiLeaks in 2016.

District Judge Vanessa Baraitser said the evidence is admissible.

Responding to the claims after the court hearing, White House press secretary Stephanie Grisham told reporters: “This is absolutely and completely false.”

The president “barely knows Dana Rohrabacher other than he’s an ex-congressman. He’s never spoken to him on this subject or almost any subject,” she said.

“It is a complete fabrication and a total lie. This is probably another never-ending hoax and total lie from the DNC.”

Assange is wanted in America to face 18 charges, including conspiring to commit computer intrusion, over the publication of US cables a decade ago.

He could face up to 175 years in jail if found guilty.

He is accused of working with former US army intelligence analyst Chelsea Manning to leak hundreds of thousands of classified documents.

The extradition hearing is due to begin at Woolwich Crown Court on Monday, beginning with a week of legal argument.

It will then be adjourned and continue with a three weeks of evidence scheduled to begin on May 18.

The decision, which is expected months later, is likely to be appealed against by the losing side, whatever the outcome.

Assange has been held on remand in Belmarsh prison since last September after serving a 50-week jail sentence for breaching his bail conditions while he was in the Ecuadorian embassy in London.

He entered the building in 2012 to avoid extradition to Sweden over sex offence allegations, which he has always denied and were subsequently dropped.

Assange appeared in court on Wednesday by videolink from Belmarsh prison, wearing dark tracksuit bottoms and a brown jumper over a white shirt.

He spoke to confirm his name and date of birth, and sat holding a stack of papers during the hearing.

The hearing came after Australian MPs George Christensen and Andrew Wilkie called on Tuesday for Boris Johnson to intervene and stop the extradition hearing.

Shadow chancellor John McDonnell is expected to become the first British MP to see Assange behind bars in a visit to Belmarsh on Thursday.

At a press conference on Tuesday it emerged that fellow inmates at the high-security prison successfully lobbied for his release from solitary confinement.

Speaking after the press conference, Assange’s father John Shipton said his son’s condition had improved, but said the extradition going ahead would be akin to a “death sentence”.