Kathryn Apanowicz dismissed actor Ricky Tomlinson's allegations and said the former Countdown host was "useless with technology" and "very indiscreet".
Tomlinson accused Whiteley of involvement in a plot to convict him for offences linked to the 1972 builders' strike in Shrewsbury.
He said the jury was swayed by a TV documentary fronted by the presenter.
In an interview given to the Chester Chronicle, at the opening of a pub, the Royle Family star said classified documents showed the then prime minister Sir Edward Heath and Labour MP Woodrow Wyatt were "involved" in a conspiracy to jail a group of striking workers, known as the Shrewsbury 24.
An ITV documentary Red Under the Bed, featuring the defendants and presented by Whiteley, was broadcast in 1973 before the jury delivered their verdict, he said.
Tomlinson, a former trade unionist, told the newspaper: "They made a film which went out on television the night the jury were out considering the verdict... and it was so anti-trade union that two of the jury changed their mind and brought a majority verdict in of 10-2 guilty.
"We found out this week that the film was designed, written, made and paid for by the security services.
"Woodrow Wyatt was a member of the security services and, unbelievably, so was Richard Whiteley who hosted the show.
"Richard Whiteley from Countdown was a member of the intelligence services."
Mrs Apanowicz defended her late partner and said: "He was the most indiscreet man I've known, he couldn't keep a secret.
"It's ridiculous. He was useless with technology. He couldn't do maths - he used to struggle with the [Countdown] Conundrum.
"When I heard this I couldn't stop laughing."
She also said Bradford-born Whiteley had "an asthma inhaler" and could not run around "escaping from whoever".
"Really and truly, Ricky Tomlinson should take a long, hard look at himself and stop casting such stupid aspersions because it's nonsense. He's made himself look a bloody fool."
Tomlinson made his claims at the pub in Chester where the strike was organised 45 years ago.
Claims broadcaster Richard Whiteley was an MI5 spy are "nonsense" and "ridiculous", his partner has said.