According to the latest Opinium poll for the Observer newspaper, Farage's newly formed party is on 34% of the vote ahead of the 23 May election that is being held because Britain failed to leave the European Union as expected in March. Prioritising intra-party politics at home over the opportunity to elect the best decision-makers would be a disservice - not just to the least privileged in the United Kingdom, but much further across the globe. If one thing will increase the chance of a hard Brexit and embolden the far right too, it's the mandate they could claim if the projected triumph of the Brexit Party winning the largest vote share in these elections is realised.
But talks with Labour to try to secure what ministers describe as the "stable majority" in parliament to get the deal, or Withdrawal Agreement, ratified, have yet to find a breakthrough which would offer the government opposition votes.
That level of support would see the Brexit Party win 49 seats, becoming the UK's second biggest party after Labour, with 137.
Sir Keir highlighted how the party lost 200 lost seats in this month's council elections, which he said were a sign Labour was losing the trust of Remain as well as Leave voters. The Liberal Democrats - who openly oppose Brexit - are just ahead of the Tories on 12%.
"The data shows the public aren't yet convinced that these newer forces will become a permanent feature in British politics, although both these parties will be hoping to prove the public wrong, and a strong showing in next week's election could give them momentum and help them stand out in an increasingly crowded field".
"And it will, it will take six to eight weeks to get the whole exercise going, but let's just start it now".
"We've got a two-party system that now serves nothing but itself", he said.
He condemned the talks with Labour and the prospect of a "Brexit in name only".
Ministerial aide Huw Merriman said the party faced a "mauling" as an opinion poll suggested the Conservatives could slump to fifth place.
Labour has dropped 5% from 21% the previous week.
He said: "I didn't expect to see him at all".
He said: "On the European elections, while the question of which party Brexit voters should back was settled some time ago, the equivalent for Remain voters is still ambiguous". Giving a vote to a minority party at these elections will be a greater gift to Farage than a kick in the face for Labour.
YouGov surveyed 2,212 adults for its survey.