The man was arrested after the 78-year-old former minister was found dead on Thursday having "sustained serious injuries".
He was detained on Friday in Newton Abbot, a town about 15km from Widdecombe's home in rural southwest England.
But on Saturday, Devon and Cornwall Police confirmed the man's release from custody.
Assistant Chief Constable Matt Longman said: "Our priority remains identifying those responsible and ensuring that all available evidence is thoroughly examined.
"Detectives continue to carry out numerous enquiries as part of the ongoing investigation and we remain committed to establishing the full circumstances surrounding the incident."
He said the investigation was "moving at a significant pace", adding: "We are deploying all of the necessary resources to find out exactly what has happened.
"I would appeal to anyone who may have information about this incident, however insignificant it may seem, to come forward and speak with us.
"We will release further information when we are able to do so. In the meantime, I would ask people not to speculate about what might have happened, particularly on social media.
Longman said there was no information to suggest the murder was related to terrorism or had a political motive.
Widdecombe was well known for her socially conservative views, first as a junior minister in Conservative prime minister John Major's 1992-1997 government and later as an immigration and justice spokeswoman for Nigel Farage's populist Reform UK.
She also found fame outside politics after starring in TV shows Strictly Come Dancing and Celebrity Big Brother.
Police said officers were called to Widdecombe's home shortly after midday on Thursday, where she was found dead.
Prime Minister Keir Starmer paid tribute to "Ann's dedication during her many years of public service".
He said that it was a moment to "rise above any political differences" and added he had spoken to his expected successor Andy Burnham, Conservative leader Kemi Badenoch and Reform UK leader Farage about the case.
Following the announcement of her death, and before details of the murder inquiry were announced, former colleagues from both the Conservative and Reform UK parties paid tribute to her.
Farage said he was "deeply, deeply upset" by the nature of Widdecombe's death.
He added: "Rest in peace, Ann. A remarkable, principled woman, and a truly dreadful way to die, and a terrible reflection on modern Britain.
Commons Speaker Sir Lindsay Hoyle, who established the Speakers' Conference in 2024 to examine the security risks faced by MPs, said: "I'm deeply shocked to learn of the circumstances around Ann's death.
Former Conservative prime minister Boris Johnson called her "a heroic Brexiteer and a great speaker who could move Tory audiences to such ecstasy that she was a very hard act to follow."
Widdecombe, who appeared on TalkTV 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".
with PA
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