Britain’s oldest think tank, the Labour party supporting Fabian Society has released a report detailing the “clear and present danger” that Ukip poses to the party’s 2015 election hopes.

The report, titled Revolt on the Left: Labour’s UKIP problem and how it can be overcome pinpoints five seats deemed to be ‘critical or high risk’ at being lost to Ukip at the next election. And whereas six Conservative seats may be lost to Labour thanks to Ukip influencing the poll, the report has found sixteen such seats that Labour may lose to the Conservatives through an indirect Ukip influence.

The slogan “Vote Ukip, get Labour” is widely used within the Conservative party to scare those of its voters thinking of switching allegiance to Farage’s party with the threat of a socialist Miliband-led government, but Ukip have long protested that they threaten all the Westminster parties.

During his recent Leader’s speech at Ukip’s Party conference, Ukip leader Nigel Farage said his party was “tearing vast chunks” out of Labour’s vote and vowed to park Ukip’s “tanks on the Labour Party’s lawn”. The Fabian’s report lends significant credibility to that claim.

The paper’s author, Marcus Roberts, details the Labour Party’s complacency towards Ukip. “Labour can’t agree on whether the problem exists or how big it is, so agreeing on a solution has proved impossible so far,” he laments.

In particular he is critical of the line of thinking that runs: as Ukip takes more votes from Tories than from Labour, the party can safely ignore them and possibly even welcome them as making a Labour victory more likely – an analysis, he warns, that is deeply flawed.

“In simple terms,” he writes, “UKIP may be taking a larger number of Conservative votes but this often occurs in seats where Tory majorities are large enough to absorb the defection. In contrast, Labour as a party of opposition needs to grow its vote dramatically to win the general election. Labour to UKIP defectors make the climb to a constituency majority harder, longer and steeper than it would otherwise be.

“UKIP are taking the discontented voters who should be the bread and butter of opposition renewal out of the electoral market.

“Direct switching from Conservatives to Labour has been very low since 2010, and Ukip are a key reason – for every four Tory switchers, three go to UKip and only one goes to Labour.”

Using data collected by Dr Rob Ford and Ian Warren, the paper categorises Parliamentary seats into risk categories. Eleven have been deemed ‘critical’ or ‘high risk’, five of which are currently held by Labour, five by the Conservatives and one by the Liberal Democrats. They are:

*Critical: Clacton (Con/Ukip); Great Grimsby (Lab); South Thanet (Con); Thurrock (Con)

*High risk: Dudley North (Lab); Eastleigh (Lib Dem); Great Yarmouth (Con); Plymouth Moor View (Lab); Rother Valley (Lab); Rotherham (Lab); Waveney (Con).

The six critical and very serious indirect threat seats that the Conservatives might lose to Labour as a result of the UKIP threat are: Warwickshire North, Cardiff North, Broxtowe, Stroud, Carmarthen West & South Pembrokeshire, and Pudsey.

The sixteen critical and very serious indirect threat seats which Labour might lose to Conservatives as a result of UKIP-Labour considerers are: Southampton Itchen, Great Grimsby, Walsall North, Plymouth Moor View, Telford, Dudley North, Halifax, Wolverhampton NE, Birmingham Edgbaston, Blackpool South, Walsall South, Leicester West, Nottingham South, Southampton Test, Birmingham Northfield, and Wakefield.

The paper also analysed all seats with a majority of under 20 percent, which it deemed “marginal”. Of these, Ukip is hurting Labour in 68 of its marginal seats, and is drawing support away from the party in a further 15 marginal Labour targets. Meanwhile, it is hurting the Conservative vote in 81 Conservative marginal seats, and drawing support away in a further 30 targets.

“The simple message is this,” the paper notes “there is no single “Ukip effect”, but instead UKIP have the power to muddy the waters across a wide range of crucial local battles.”

The paper also highlights a shift in the impact that Ukip is having, as it turns from drawing away Conservative support, to drawing support from ex-Labour voters.

“As Professor Stephen Fisher has noted, between 2010 and 2012, UKIP gained more from ex-Conservative voters. But from 2012 to 2014 has gained more from ex-Labour voters. In other words, statistical evidence suggests that UKIP is a decreasing problem for the Conservatives and an increasing problem for the Labour party.”

As for solutions, an overhaul in terms of policy, messaging and organisation on the ground is strongly recommended if Labour is to overcome the Ukip threat, with the author urging a move to “blue collar policies”.

In particular he is critical of Labour’s move away from the working class vote, which he sees as central to the loss of votes to Ukip, and rejects John McTernan’s suggestion that Labour embrace a progressive liberal urban vote, calling the idea “callous” and “a betrayal of Labour’s traditional working class vote”.

This morning, a YouGov poll put the Conservatives one point ahead with only eight months to go until the general election. What is becoming increasingly clear is that, thanks to Ukip, the outcome of that election will most likely be anyone’s guess until the final results are in.