Widdecombe was a Conservative MP between 1987 and 2010, and held several junior ministerial positions in former prime minister John Major's government.
She later became a Brexit Party MEP and subsequently a Reform UK spokeswoman.
Widdecombe also found fame outside politics after starring in the TV show Strictly Come Dancing.
"Our murder enquiry is in its early stages but moving at a significant pace," Devon and Cornwall Police said in a statement.
"We are deploying all of the necessary resources to find out exactly what has happened and to locate the person responsible who we believe to be a white male."
Police said they were called to Widdecombe's address about midday on Thursday where she was found to have died and sustained serious injuries.
"A cordon remains in place at the property while specialist officers continue forensic examinations," the statement said.
Widdecombe, who appeared on Talk radio on Wednesday, lived in Haytor, near Newton Abbott in Devon.
UK Home Secretary Shabana Mahmood urged the public not to speculate, describing the circumstances as "extremely distressing".
In a post on X, Mahmood said: "I am deeply saddened to hear of the death of Ann Widdecombe. The circumstances of her death are extremely distressing and my thoughts are with Ann's family and loved ones".
"I urge everyone to avoid speculation and allow the police investigation to progress."
Prime Minister Keir Starmer said it was "really shocking news" that police had launched a murder investigation.
It was a moment to "rise above any political differences" and said he had spoken to leading politicians Nigel Farage, Andy Burnham and Kemi Badenoch.
Starmer urged anyone with information to help police get the suspect into custody.
with PA
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