Zac Goldsmith, the Conservative MP for Richmond Park, has clashed angrily with broadcaster Jon Snow during a live TV interview about claims the millionaire Tory broke the rules on election spending.

Goldsmith accused Snow of telling viewers "deliberate and outrageous" lies and warned Channel 4 News to "watch it" during a finger-wagging 13-minute appearance on the 7pm show.

At one point Goldsmith – who has the backing of the Conservative party over the allegations – leaned over the desk and pointed at Snow, protesting: "You are being a charlatan on this."

A clearly annoyed Snow responded by telling the MP he was "in trouble" and advised him that if he had a complaint about Channel 4 News he should go to the independent regulator Ofcom.

The squabble followed an investigation by Channel 4 News and the Bureau of Investigative Journalism into campaign spending at the last election.

In a report that aired on Thursday, Channel 4 News raised doubts over how Goldsmith kept his spending within the legal limit set by the Electoral Commission.

Snow told viewers that Goldsmith ordered 272,000 posters and leaflets, which invoices show cost more than £14,000 – a figure well over the £11,003 spending limit. But the cost was reduced after his campaign team declared he did not use 62,000 of the posters, which reduced his spending declaration by more than £2,500.

Goldsmith – whose fortune is estimated at £200m – filed a detailed declaration of his spending in June, putting the total £220 below the cap at £10,783.

Goldsmith appeared in the Channel 4 News studio last night to defend the claims, but insisted Snow first apologise for telling viewers he had "bottled out" of an interview on Thursday. He said: "I think the viewer will be very interested to know that you misled them deliberately."

The interview degenerated into a near slanging match before Goldsmith said it was now up the Electoral Commission to decide on one of three options. "Either they will decide not to look at it, in which case you want to watch it. Or they will decide to look at it and give me a green, light, in which case you want to watch it. Or they will look at it and find out there's something wrong ..."

Snow interrupted: "In which case, you'll have to watch it."