Mrs Leachman said the first Robins Pie & Mash shop was set up in London nearly a century ago and the family owned six businesses across east London and Essex.
She said pie ‘n’ mash shops were a “way of life” and a “tradition” for people with an east London heritage.
“We want to protect what my past generations worked so hard for,” she told the BBC.
“We don’t want it diluted and being sold anywhere and with any recipe.”
She said pie ‘n’ mash was made to a “specific” recipe: minced beef, mashed potatoes, and liquor – a parsley sauce.
“That’s how it should remain,” she added.
“In here, that is what we believe in, and that’s what all other pie ‘n’ mash shops are – and we should protect that as much as we can.”
Mr Holden said, before the debate, that he had written to more than 40 MPs who had a pie ‘n’ mash shop in their constituency.
“It’s part of a campaign to celebrate and really promote pie and mash, which has spread out from its beginnings in central and east London, down the Thames Gateway and out into the world,” he had said.
“We’re wanting to celebrate it.”