In the general election on 12th December 2019, only a 47% minority of votes were for pro-Brexit parties. The democratic wish of the remaining 53% majority must be respected. Therefore hold a first-time referendum on the UK's post-2020 relationship with the EU, including an option to rejoin the EU.
You may be interested in these active petitions
Although first-past-the-post is an established system for electing MPs, and consequently a prime minister, it failed to determine correctly in December 2019 whether a majority of UK and Gibraltar voters support leaving the EU with the withdrawal agreement. The only reliable indicator of this is the total votes for each side of the argument, as was used in June 2016 when the electorate held a different opinion from now. Although the transition period is a fait accompli, the rest of Brexit is not.