The behaviour of Matt Hancock was an issue on the doorstep in the Batley and Spen by-election, the Tory Party co-chair has admitted.
Mr Hancock resigned as health secretary after CCTV footage emerged of him kissing a close aide in his office in breach of social distancing rules.
Initially when the story broke last Friday, Boris Johnson stood by him, accepting his apology and insisting the matter was closed.
However Mr Hancock was forced resign the following day after Conservative MPs made clear his position had become untenable.
Amanda Milling, the party co-chair, acknowledged his conduct had been an issue in the final stages of the by-election campaign.
“It was something that came up on the doorstep, I have to be honest about that. They (voters) had some issues over the weekend in terms of what happened,” she told Sky News.
She added: “I know the public will be incredibly frustrated because at the end of the day we have all made a huge number of sacrifices. But Matt did the right thing by resigning. The matter is now closed.”
Her comments are likely to lead to frustration among Conservative activists after the party came within 400 votes of winning in Batley and Spen, delivering a body blow to Labour leader Sir Keir Starmer.
It will raise questions over whether the party could actually have taken the seat if the Prime Minister had sacked Mr Hancock when the news first broke.
Ms Milling said that it had been a “tremendous result” for the Tories to get so close in a constituency which Labour held with a 3,525 majority at the 2019 general election.
“It was a very, very close result. This is not a great win for the Labour Party. They have only won by a matter of just over 300 votes,” she said.
“Governing parties don’t gain by-elections and actually taking it to such a small number of votes is in itself a tremendous result.”
She insisted that Mr Johnson remained very popular among voters.
“There is a lot of love for the Prime Minister. He gets a tremendous lot of support on the doorstep,” she said.
Meanwhile Labour is continuing to press for answers as to whether Mr Hancock followed proper procedures when he appointed Gina Coladangelo to the board of the Department of Health and Social Care for £15,000-a-year for just 15 days’ work.
She has since also resigned from the department.