The prize-winning journalist, who was injured by flying shrapnel in 1992 while covering the Bosnian war, put himself forward a few days ago after the Labour candidate, Jon Kelly, had said he would stand aside in favour of a respected non-party outsider to challenge Mr Hamilton, the MP at the heart of the cash-for-questions affair.
The Liberal Democrat candidate, Roger Barlow, quickly followed suit yesterday. Mr Bell attended separate meetings with both parties in the constituency.
A senior Labour source said last night that both local parties had been "very impressed" by Mr Bell, who will hold a press conference to formally announce his candidature today.
Mr Bell's challenge adds to the already severe pressure on Mr Hamilton to stand down, or to get his local Conservative association to dump him, pending the verdict of the parliamentary inquiry into the cash-for- questions allegations that have been levelled against him.
If Mr Hamilton does give way, then there will be no reason for Mr Bell to stand, and Labour and the Liberal Democrats will return to the election fray - to fight the replacement Tory candidate.
However, if it is left to Mr Hamilton and he is challenged by Mr Bell, there is agreement within the constituency, and in the polls, that the non-party candidate might well be able to wipe out the Tory's seemingly unassailable majority.
The notional majority in the re-drawn constituency is 22,000, requiring a by-election style swing of almost 22 per cent to oust the Conservatives.
Tatton Tories gather tomorrow night for a meeting which would have been a formality - the adoption of Mr Hamilton as their candidate. That is thrown into doubt by Mr Bell's intervention.
The BBC said last night that Mr Bell had been placed on unpaid leave for the duration of the election campaign and that BBC rules prevented him from returning to work in current affairs. His position would be reviewed after the election.
Last night, a source close to Mr Bell said one of the reasons he had decided to put his name forward was because of his admiration for Paddy Ashdown's commitment to solving the problems in Bosnia.
Labour's lead over the Conservatives remains unchanged since last week at 21 per cent, according to the latest Gallup poll in today's Daily Telegraph.Reuse content