Lynch, who leads the RMT union, appeared on the show last night to explain why 40,000 railway workers are striking for three days this week, including today.
The walkout is the largest seen in the UK for more than 30 years and means only 20% of services will be operating during the industrial action.
The RMT union said it has “no choice” but to strike over stagnant pay, job losses, work conditions and threats to pensions after 11th-hour talks with railway operators failed.
On Monday night, Newsnight’s presenter Kirsty Wark asked technology minister Chris Philp why the government was not getting more involved in a bid to resolve the conflict last night.
″Mick Lynch has previously said he would not negotiate with a Tory government,” Philp claimed.
“That’s a lie,” Lynch said from the other side of the panel. “That’s a direct lie.”
Philp pushed on: ″The head of the rail delivery group this morning on the Today programme said he didn’t want the government in the negotiation.
″We’ve made money available to the railway industry, it’s up to the employers to negotiate with the trade unions and what happened this afternoon is that halfway through those negotiations, while they were ongoing, the unions came out –”
“That’s a lie,” Lynch said again.
″– came out onto the street and gave an impromptu press conference saying the strike was going to continue.”
In response to Lynch’s repeated claims that his claim was a lie, the minister said, “it was on video”.
“It wasn’t on video at all, that is a lie.”
Lynch claimed he would “absolutely” be prepared to negotiate with a Tory government.
“I have met every transport minister in the last year – bus, rail, maritime and the secretary of state. We’ve never said we won’t meet the Tories.
“What we’ve said is that they’re not at the table when negotiating with the employers.
“You’ve also lied we left negotiations on Saturday and went to a rally.
“There were no negotiations scheduled for Saturday – you are a liar.”
The minister claimed that it was all caught on video tapes, but Lynch said: “And then we went back to the talks,” adding one more time: ″You are a liar.”
Chief secretary to the Treasury Simon Clarke did actually address why the government was trying to stay out of the strikes on Monday.
He told Sky News: “We don’t control all the levers that need to be held here as the employer.
“The employer is Network Rail and the train operating companies.
″They’re the ones who need to drive the programme of reform, they’re the ones who need to make the railways sustainable.
“We don’t own the railways ourselves, and it wouldn’t be right for us to substitute ourselves for the role of the employer.”
However, he also said that public sector workers would not be getting a pay increase in line with inflation – currently at 9%.