Labour officials have briefed that they will not put resources into fighting seat, angering party activists who say it is winnable

Ed Miliband is under pressure to make a strong attempt to deliver a Labour victory in the Rochester byelection, with party activists venting their frustration at what they regard as defeatist signals coming from party headquarters.

Miliband has been under fire since a bungled speech to the party conference in which he omitted any mention of the budget deficit. YouGov polls have shown the Tories leading Labour for the past three days, and the Labour leadership will be watching anxiously over the next week to see whether David Cameron is benefiting from a temporary conference bounce or whether there has been a longer-term change in the political weather.

Labour is optimistic on the basis of published polls that it will win the Heywood and Middleton byelection on Thursday, seeing off a challenge from Ukip, and expects the Conservatives to lose Clacton.

But there is undisguised fury among some party activists that senior party figures are playing down their chances of winning Rochester in a byelection brought about by the defection of the Tory MP Mark Reckless to Ukip.

The Tories have not yet set a date for the byelection but it is expected to be held next month. Labour officials have briefed that they will not be putting resources into fighting the seat.

Senior figures pointed out that the seat lies at 129 on the party’s list of targets, outside the 106 that Labour is focusing most resources on. They said a Labour victory would require the Tory vote to split with half going to Ukip, and for Labour to gain support without losing any 2010 votes to Ukip.

Writing on LabourList, Luke Akehurst, a former member of the party national executive, said: “The job of party high-ups be they officials or senior politicians is to devise strategies, tactics and messages that stop our vote going to Ukip and attract additional support to Labour, rather than issuing defeatist briefings that undermine the CLPs [constituency Labour parties] and candidates in the frontline.

“If they don’t have the audacity and self-belief to win, they need to resign and let people with some fire in their bellies give it a go. The analogy here isn’t lions led by donkeys, it is lions being briefed against by chickens.”

He continued: “At the moment we seem to have an electoral strategy designed by Mr Micawber. ‘Something will come along’ (the tooth fairy?) to gift us a narrow victory on a 35% vote share thanks to flaws in the voting system.”

He said that if the party won on that basis, it would “have no real mandate to take tough decisions in government, or need to auction our souls and our manifesto commitments to Nick Clegg to get a majority.”

He added: “We have just over six months left to work out if we actually still want to be the party that represents the hopes and aspirations of the British working classes or if we are prepared to give up that role to Ukip. A good starting point would be to look at the top level of the party like we want to win in Rochester.

“We might not do it but we would send a signal that we wanted the support of and cared about those voters. Our mentality this close to general election ought to be that we are an unstoppable force, not a party too scared of Nigel Farage to take him on in a seat we held until the last election.”

Akehurst pointed out that one poll in Rochester published by Survation put Ukip on 40% (+40 since 2010), the Tories on 31% (-18), Labour on 25% (-3) and the Lib Dems on 2% (-14). Excluding people who did not vote in 2010 and were therefore highly unlikely to vote in a byelection, where turnout is almost always lower, the Tories and Ukip were on 34% and Labour was only six points behind, on 28%.