The clue to what Jeremy Corbyn ought to be doing for a living is in his job title: Leader of the Opposition. The Labour Party's members, MPs and their traditional voters – not to mention vast swathes of the population who deserted their own parties to vote for Corbyn at the last General Election – all counted on him to do what is right on the issue of Brexit. First, to hold the government to account in the way they handled the process, and, now that the country is facing the clear and present danger of a No Deal Brexit, to take a decisive, commanding opposition stance to end this shambles.

His failure to do so can be seen in the figures that have just been released by my tactical voting campaign website Remain United. The independent analysts I commissioned from Electoral Calculus, using new polling undertaken by ComRes, found that with no change in its current position on Brexit and no tactical voting, Labour would win 20 seats in Thursday’s European elections, with the Brexit Party taking 28, the Conservatives 6, the Lib Dems 11, and the Green Party 1.

If, however, Labour were to come out with a clear pro-Remain and decisive second referendum position, its seat share would rise dramatically to 35 out of the total of 70 – overtaking the Brexit Party, who would return just 23 MEPs. The gap in the two sets of figures for Labour might reasonably be blamed on Mr Corbyn. This is what the research clearly shows.

But it’s the Opposition that I hold accountable for this mess. I sometimes wonder if this one has any real appetite to take office. Corbyn's position on Brexit – studied ambiguity, if not studied inertia – looks more and more like a conscious act of turning voters away. The polling figures bluntly show that if Corbyn were to take a principled stand against Brexit, it would transform his party's electoral performance in every region of Great Britain, including its Northern England heartlands.

If Labour changed its position – and just half of voters supporting Remain parties then felt able to support Labour, instead of other Remain parties – the party would take a vote share of 45 per cent: beating the Brexit Party’s share by half, and that of the Conservative Party by more than four times over.

I would go so far as to say that ignoring these findings amounts to a gross dereliction of duty on the part of Mr Corbyn and an unforgivable betrayal of the legitimate hopes and aspirations of Labour voters. It will be the less well-off and vulnerable in our society that will be hit hardest in any ensuing economic downturn – the very people who were once able to rely on Labour to put their interests first.

With the opposition failing to oppose, I can only emphasise once again how important it is for people to vote tactically in tomorrow's all-important EU elections. Remain-supporting voters have four options spelt out on our Remain United website, but in essence:

In Scotland and Wales, nationalists who support remaining in the EU can vote for the SNP or Plaid Cymru, while non-nationalists can vote for the Liberal Democrats, as both parties in each can win their maximum seat haul without the need for pro-Remain voters to choose between them.

In the South West and South East of England, the West Midlands, and Yorks/Humber, pro-Remain- voters should choose between the Lib Dems or the Greens, as both can win seats here

In Eastern/Anglia, the East Midlands, London, the North East, and the North West, the clear advice is to vote Lib Dem.

Even at this 11th hour, if Labour were to come out clearly against Brexit, the poll findings show seat gains would be made by the party in almost every region of Great Britain, including, significantly, in areas which voted Leave in 2016: in the West Midlands, Labour’s seat share would rise from 2 to 4; in the North West it would rise from 3 to 5; and in Wales it would rise from 1 to 3. In areas that voted Remain in 2016, Labour’s haul of seats would double: in London it would rise from 3 to 6, and in Scotland it would rise from 1 to 2.

Nigel Farage apparently takes victory very much for granted in the EU elections, but it is still within the power of remain voters, even now, to wipe the smirk from his face. What cheers me up enormously is that the turnout tomorrow looks like it will be big. Pollsters tell me that where previously around 35 per cent turned out for the EU elections, this time the figure is projected to reach 48 per cent. Some 49 per cent of 18-24s are expected to vote, while turnout among the over-65s is expected to reach 65 per cent. There is clearly still everything to play for.

Gina Miller is the founder of www.remainunited.org