Speaking at a press conference in a small theatre in Knutsford, also in Cheshire, hours before the Labour candidate he is replacing was due to formally stand down, Mr Bell said he had made his decision "with a bit of a sad heart".
"But," he added, "it became clear, especially now I'm in for the long haul, that I could not remain even theoretically or technically a BBC reporter.
"I'm not going back. I expect to be the next MP for this constituency so I have necessarily burnt my bridges behind me."
Tony Hall, the chief executive of BBC News who had previously refused the reporter's resignation in November, had taken it well, Mr Bell said, and "with a certain degree of relief".
The veteran reporter had requested that his "BBC swan song", a documentary on the United Nations, and a series of radio pieces entitled The Truth is our Currency, be broadcast as planned.
But Mr Bell revealed that he had, that morning, made a formal complaint to his former employer about the coverage of his campaign.
While he had been canvassing in Wilmslow, the BBC had chosen to broadcast footage of one person of the three who had opposed him, instead of the 25 who had offered their support. "I never thought I'd been in this situation," he joked. "I left the Beeb and already standards declined so fast?"
Mr Bell also revealed that he had a new political ally in the form of the former Manchester police chief John Stalker, famous for his anti-corruption stance, who had approached him yesterday to offer his support.
"He came in off the street this morning," Mr Bell said. "Mr Stalker was out for a walk on the heath and he called us.
"I'm very, very pleased as he's Mr Integrity and his endorsement carries some weight in these parts."
After the Conservative candidate Neil Hamilton's official reselection on Tuesday night, at least one local Conservative councillor resigned in protest at a vote some protested was "a whitewash".
They raised prospects of an independent Conservative candidate to stand against Mr Hamilton, a possibility that appeared to have been firmly squashed from above by yesterday afternoon.
Mr Bell said that following the vote, he had received a number of calls from Conservatives, the identity of whom he hoped to be able to reveal in the near future.
"[Their calls] are very important to me. I've been spending a lot of time talking to these people," Mr Bell said.Reuse content