Boris Johnson has refused to get involved in the case of British software entrepreneur Mike Lynch, who faces a hearing next month on possible extradition to the US over alleged fraud.

Mr Johnson suggested last year that a UK-US extradition agreement was “unbalanced” and he is facing pressure from former cabinet ministers to intervene in the case to keep Mr Lynch in the UK.

But Number 10 said on Tuesday that Mr Johnson had looked at the extradition agreement to “make sure the system is working as it should”. A spokesman for the prime minister said: “He is confident that is the case.”

Mr Johnson’s spokesman added: “As is usually the case, given that it is before the courts, it would be inappropriate for me to comment further.”

The comments from Number 10 will avoid the possibility of an early clash with Joe Biden’s new administration, but will be a disappointment to Mr Lynch and his high-profile supporters.

Mr Lynch is facing the possibility of extradition to the US to stand trial on criminal charges including 14 counts of conspiracy and fraud over Hewlett-Packard’s $11bn acquisition of UK technology company Autonomy in 2011.

On Tuesday five former cabinet ministers wrote to The Times warning that the government had “surrendered sovereignty” over extraditions to the US.

Four senior Tories — Andrew Mitchell, David Davis, Lord Maude of Horsham and Lord Deben — were joined by Vince Cable, the former Liberal Democrat business secretary, arguing that “the British legal system is quite capable of dealing with this [case]”.

They added: “The government cannot stand by as another Briton risks being delivered like this to the US justice system.”

Mr Lynch is fighting the US extradition request, which will be heard by a judge starting on February 8.

He is currently on bail and as part of conditions imposed last year he has had to lodge £10m security with a London criminal court and abide by other requirements including surrendering travel documents.

Hewlett Packard Enterprise (HPE) has been suing Mr Lynch in London’s High Court in a civil case claiming that the entrepreneur and his former colleague Sushovan Hussain were behind a fraudulent manipulation of Autonomy’s accounting information on a massive scale, leading to HP paying an extra $5bn for the company.

Mr Lynch and Mr Hussain have denied any wrongdoing. A High Court ruling on the case is expected later this year. There have been concerns that the US authorities have persisted with the criminal charges against Mr Lynch even though the UK's Serious Fraud Office investigated the case and opted not to bring charges.

There have long been complaints that the US-UK extradition treaty is imbalanced and favours the long arm of the US justice system. MPs have become concerned that the 2003 extradition agreement signed with the US in the wake of the 9/11 attacks is being used to target alleged white-collar suspects as well as terrorists.

The US system differs from that in England because of pressure to do a plea-bargain deal with American prosecutors rather than fight allegations in a jury trial. Around 97 per cent of criminal cases are settled by plea in the US.

In one of the highest-profile examples of extradition, US authorities targeted three former NatWest bankers to face US criminal charges linked to collapsed energy firm Enron.

The US charges were launched even though the UK’s SFO had investigated and declined to prosecute the case. The three men were extradited to the US in 2006 and agreed to a plea bargain before serving time in a US jail. All three are out of prison now.

US-UK extradition arrangements were last reviewed in 2011 by Scott Baker, a retired British judge who concluded the rules were “completely balanced”.

But many MPs have been outraged at the inability of the UK authorities to extradite Anne Sacoolas, an American woman currently in the US who is accused over the death of teenager Harry Dunne in a road traffic accident in England.