Shoppers were stunned as Solihull MP Lorely Burt clashed with a rival in a branch of Morrisons.
The Liberal Democrat crossed swords with Tory Julian Knight when he dubbed himself a “shadow MP” during an advice surgery at the store.
Mr Knight demanded an apology after accusing Mrs Burt of “aggressively” quizzing him in full view of supermarket customers.
But she hit back, saying she was responding to claims from a voter that Mr Knight was “passing himself off as the MP”.
Mr Knight – Conservative candidate for Solihull at next year’s general election – admitted he called himself a “shadow MP” during the surgery, also attended by two Tory councillors.
He said he did it to “make it abundantly clear” he was not the MP.
Mr Knight said: “Mrs Burt started taking lots of photographs of our little community stand and aggressively questioned me over my right to be in a supermarket meeting the public.
“I don’t think it is right that we should be treated this way.
“I will be writing asking her to apologise for interfering in this way and asking her to ensure it doesn’t happen again.”
But Mrs Burt called Mr Knight’s allegation “daft” and “over-blown”.
A spokesman said: “Lorely called in to Morrisons in response to a call from a constituent who said the Conservative candidate was passing himself off as the MP. It was nothing more than a friendly back-and-forth between two political rivals – far more tame than most discussions in the House of Commons. Morrisons is a great local supermarket and is to be commended for allowing its foyer to be used by local councillors for advice surgeries.
“In the meantime Lorely, as the actual MP for Solihull, holds advice surgeries every Friday, either in Solihull Connect or Shirley Police Station.
“If anyone wants any help or support, they should get in touch.”
A Morrisons spokeswoman said: “Elected MPs and councillors often run advice surgeries in our stores, because so many people pass through our doors and we are a key part of the community. On this occasion Mr Knight asked to join the two local councillors at their surgery.
“We ask that these visits are not used for campaigning purposes.”