Boris Johnson is under pressure ahead of the crucial North Shropshire by-election, as the Liberal Democrats use a photograph of leading Conservative Shaun Bailey not sticking to social distancing rules on a new Facebook advertisement.

       Voters go to the polls in Owen Paterson’s former seat on Thursday, after the resignation of the former environment secretary amid a row over his lobbying work.

       Mr Paterson, who won 62.7 per cent of the vote in the 2019 General Election, quit after a backlash to Downing Street attempts to reform the standards system, so he could avoid a recommended six-week suspension.

       The Conservatives have held the seat since 1983. However, the Liberal Democrats are now promoting a Facebook advert that includes a photograph of Shaun Bailey, the former Conservative mayoral candidate, failing to adhere to social distancing rules at a party last December.

       The caption reads: “The Conservatives think the rules don’t apply to them. Tell them the party’s over. Vote Liberal Democrat this Thursday to send a message.”

       Mr Bailey’s campaign organised the event in the basement of the Conservative Campaign Headquarters while London was under Tier 2 rules, which banned social mixing between households.

       He stepped down from his role as chairman of the London Assembly police and crime committee on Tuesday after a photo was published by the Daily Mirror.

       A spokesman for the Conservatives said formal disciplinary action was taken against four CCHQ staff who were seconded to Mr Bailey’s campaign. The Prime Minister’s official spokesman said that the party had not been aware of the event before it took place.

       Increased attention is being paid to the outcome of the North Shropshire vote in the wake of the row about Parliamentary standards and a series of allegations about reported Christmas parties at Downing Street during last December’s lockdown.

       Asked by MailPlus whether Boris Johnson was “a man of honesty and integrity”, Dr Neil Shastri-Hurst, the Conservative candidate for North Shropshire, refused to answer four times before saying he had “no reason to question” Mr Johnson's integrity on the issue of alleged Christmas parties.

       On Sunday, Nadhim Zahawi, the Education Secretary, told Times Radio that by-elections have “historically been used as a protest vote because people know it’s not going to change the outcome of which party governs the country, but actually they want to send a message for whatever reason”.

       Meanwhile, Labour volunteers were reported to have taken holiday from their jobs this week in order to travel to the constituency and campaign.

       Last week, two Conservative councillors in the North Shropshire constituency defected from the party to join Richard Tice’s Reform party and Laurence Fox’s Reclaim party respectively, both of which are standing in the by-election.

       Asked whether the Conservatives would keep hold of the seat, the Prime Minister’s press secretary said that the party was “fighting for every vote”.

       She confirmed there were no further plans for the Prime Minister to go to North Shropshire on polling day after he visited on December 3.