By Lord Ashcroft

There is a week to go in the battle to succeed Paul Goggins as the MP for Wythenshawe & Sale East. A lot can change in a week – especially the last week of a by-election campaign – and any poll is a snapshot not a forecast.

But according to a survey I completed yesterday, Labour’s grip on the seat is firm. I found Labour on 61% of the vote with UKIP second on 15%, the Conservatives on 14% and the Liberal Democrats fourth on 5%.

UKIP’s vote share will be lower than some expect, and they may be inclined to blame the methodology. I should point out, then, that for this poll I adopted the approach of prompting for UKIP along with the three main parties in the initial voting intention question. There remain good reasons not to do this in national polls, but it makes sense in a by-election like this one, where the party is receiving a great deal of attention and its candidate is treated as a principal contender.

The results represents a 17-point increase in Labour’s vote share since the last election, with the Tories down 12 points, and the Lib Dems down 17. UKIP have more than quadrupled their vote share in the constituency since 2010 – but if there is to be a surge to take the seat it is either very late or a long way below the radar.

Not surprisingly, those who have switched to UKIP – largely but by no means exclusively from the Tories – are more likely than most to say they are voting tactically to try to stop another party from winning. They are more likely still to say they are voting as a protest: nine in ten of them say they want to show they are unhappy with all the main parties at the moment.

Despite Labour’s huge overall lead, only a minority of voters in the constituency (43%) say they would rather have Ed Miliband as Prime Minister than David Cameron. In fact, a quarter of Labour voters (and more than half of UKIP supporters) say either that they are satisfied with Cameron or that they prefer him to the alternative.

When it comes to the economy, voters are more likely to say they think things will get better over the next year for the country as a whole (and only 29% think that) than to expect any improvement for themselves and their families (19%).

Even so – and again, despite the crushing margin for Labour in voting intention – Miliband and Ed Balls are only five points ahead of Cameron and George Osborne (40% to 35%) on being trusted to manage the economy in the best interests of Britain. One in five Labour voters trust the PM and Chancellor more than their own party’s team.

As for the campaign on the ground, UKIP are making their presence felt. Nearly half (47%) of voters in the constituency say the party has put literature through their door, compared to 63% from Labour, 35% from the Conservatives and 18% from the Lib Dems. They are almost keeping pace with the bigger parties when it comes to direct mail and street campaigning – though, like the Tories, are further behind when it comes to knocking on doors.

We will see in seven days whether their activity can do anything to loosen Labour’s grip.