2015 UK General Election Forecast by ElectionsETC.com

Labour stay 1 point ahead of the Tories in our polling average (34%–33%), but both UKIP and the Lib Dems are down a point to 13% and 8% respectively. (In the Lib Dems’ case, that’s just a reversal of the 1 point gain they made last week.)
Our central forecast therefore still has the Conservatives winning 34% of the vote to Labour’s 32%, but UKIP down to 12% (from 13% last week) and the Lib Dems on 10%.
The latest Scotland poll from TNS is very good for the SNP, moving them up a point in our Scotland forecast. Our central forecast now has them winning 47% of the Scottish vote and 51 seats (up from 46% and 49 seats last week).
With time running out to pull ahead, the Conservatives’ chances of a majority are down to 8% (from 10% last week) while Labour’s are still just 1%. The chances of a hung parliament are therefore up again, to 91%.
Our central forecast has the Conservatives winning the most seats, with 286 to Labour’s 265, but falling well short of a majority. In this scenario, even the Lib Dems and the DUP would not be enough to give them 323 MPs. This would put us in the “Con largest,but Lab+SNP+others maj” segment on the pie chart above – an outcome our model gives a 20% chance of occurring.

Date of forecast: 15 April 2015
Days till the election: 22
Inputted current average poll shares
Con: 33%
Lab: 34%
LD: 8%
UKIP: 13%
Others: 12%
Forecast GB Vote Shares (with 95% Prediction Intervals)
Con: 34% (30% – 38%)
Lab: 32% (29% – 36%)
LD: 10% (6% – 14%)
UKIP: 12% (8% – 16%)
Others: 11% (10% – 13%)

Forecast Scotland Vote Shares (with 95% Prediction Intervals)
SNP: 47% (43% – 51%)
Labour: 28% (24% – 32%)
Forecast GB Seats (with 95% Prediction Intervals)
Con: 286 (245– 330)
Lab: 265 (224 – 304)
LD: 23 (14 – 32)
SNP: 51 (42 – 57)
PC: 3 (2 – 3)
UKIP: 4
Grn: 1
(May not sum to 632 due to rounding of sums of probabilities.)
Central forecast: Con short of a majority by 37
(Criterion for majority now changed to 323 not 326, assuming Sinn Fein win 5 seats and do not take them.)
Probabilities of key outcomes
Con most votes: 65%
Lab most votes: 35%
Con most seats: 67%
Lab most seats: 33%
Hung Parliament: 10%
… with Con largest: 59%
… with Lab largest: 32%
Probabilities of predicted government outcomes:
(See here for explanations and assumptions)
Con majority: 8%
Con+DUP: 6%
Con+LD: 14%
Con+LD+DUP: 14%
Con largest, but Lab+SNP+others maj: 20%
Con largest, but Lab+SNP maj: 5%
Lab largest, Lab+SNP maj: 9%
Lab+LD+DUP+SDLP+PC+Grn+Hermon: 8%
Lab+LD+DUP: 8%
Lab+LD: 7%
Lab+DUP: 1%
Lab majority: 1%
(Probabilities may not sum due to rounding)