The by-election came days after Mr Hancock was forced to step down as Health Secretary after admitting he had broken social-distancing guidelines when caught in a clinch with his aide, Gina Coladangelo. He still faces questions over her employment at taxpayers’ expense.
Conservative Party co-chair Amanda Milling acknowledged the behaviour of Mr Hancock had been an issue during the by-election, telling Sky News: “It was something that came up on the doorstep, I have to be honest about that.
“They had some issues over the weekend in terms of what happened. Matt resigned and that was the right thing to do.”
In an awkward exchange with presenter Kay Burley, Ms Milling refused several times to say whether Mr Hancock’s actions were subject to an investigation. She said the Tories’ failure to win was “disappointing” but insisted it was not a “great win” for Labour.
Election guru and Conservative peer Lord Hayward said it was “reasonable” to suggest that the Hancock scandal had contributed to the Conservative Party’s narrow defeat. He said: “With a small majority, a small defeat like this, you can always point to things which made a difference and I think it’s reasonable for people to say well with a small majority this might have influenced the results.”
Supporters of Labour’s deputy leader Angela Rayner were said to have been plotting a move against Sir Keir if another seat turned blue after the Tories snatched Hartlepool in an historic by-election two months ago.
Labour’s Kim Leadbeater, whose sister Jo Cox served as the constituency’s MP before she was murdered by a neo-Nazi in 2016, won the seat.
The contest had been marred by allegations of dirty tricks and attempts to divide voters on racial grounds.
Labour’s vote share has been consistently falling in the constituency in recent years and was compounded at this by-election by controversial former Labour MP George Galloway, who won nearly 22 per cent of the votes.
The Prime Minister stood by Mr Hancock when the scandal broke last Friday, with his spokesman telling journalists he accepted his apology and considered the matter “closed”. However, amid mounting pressure from the public, Mr Hancock resigned as Health Secretary on Saturday.
Asked whether the Prime Minister’s actions could have impacted the result, Lord Hayward added: “I think it’s a combination of both sides. It’s not just Matt Hancock. It is a decision of the Prime Minister because of the apparent delay in taking action.
“So, when you lose an election, particularly by a small margin you can point to all sorts of different things, but clearly that will be something that will come up.”
Labour heavyweight Lord Mandelson said: “Well, inevitably it was brought up on the doorstep. It was a colossal piece of hypocrisy by Matt Hancock, but also a colossal misjudgement by the Prime Minister.
“It says something about him, doesn’t it? He feels that somehow he and his government are above the rules that everyone else has to live with. That somehow the rules, the laws don’t apply to them.”
Labour’s national campaign co-ordinator Shabana Mahmood said there were “still questions” for the Government to answer over the scandal, adding: “We will certainly be pressing the Government to answer them.” Ms Leadbeater secured the seat with 13,296 votes while Conservative candidate Ryan Stephenson came second with 12,973 and the Workers Party’s Mr Galloway came third with 8,264.
Sir Keir said Ms Leadbeater won the election “against the odds” and added: “Kim has shown inspiring resilience in the face of hatred and intimidation.”
Ms Leadbeater told the BBC: “It was a very big decision to put myself forward. It has been a very emotional campaign and today is very emotional for me for lots of reasons.
“But if I can be half the MP Jo was I know I will do her proud, and I will do my family proud.”
Mr Galloway said he would apply to have the result set aside by the courts.
Speaking outside the count, he said his election effort had been damaged by a “false statement” that he had laughed while Ms Leadbeater was abused on the campaign trail.