Share of seats and votes in UK General Elections since 1945

Percentage vote

Year	45	50	51	55	59	64	66	70	74F	74O	79	83	87	92	97	01	05
Cons	40.26	43.44	47.97	49.74	49.36	41.84	40.49	44.89	37.77	35.73	43.87	42.44	42.23	41.93	30.66	31.7	32.36
Lab	47.88	46.11	48.78	46.21	43.68	43.76	47.57	42.68	37.22	39.25	36.85	27.58	30.84	34.39	43.21	40.7	35.19
Lib	8.99	9.11	2.55	2.72	5.89	11.2	8.62	7.47	19.34	18.32	13.82	25.38	22.54	17.85	16.76	18.3	22.05
Other	2.87	1.34	0.7	1.33	1.07	3.2	3.31	4.95	5.67	6.7	5.46	4.60	4.39	5.83	9.37	9.3	10.4

Percentage of seats

Year	45	50	51	55	59	64	66	70	74F	74O	79	83	87	92	97	01	05
Cons	33.59	47.68	51.36	54.76	57.94	48.09	40.17	51.11	46.61	43.46	53.39	61.08	57.69	51.61	25.04	25.2	30.65
Lab	61.72	50.4	47.2	43.97	40.95	50.32	57.62	45.72	47.56	50.24	42.2	32.15	35.23	41.63	63.43	62.5	54.95
Lib	1.88	1.44	0.96	0.95	0.95	1.43	1.9	0.95	2.2	2.05	1.73	3.54	3.39	3.07	6.98	7.9	9.6
Other	2.81	0.48	0.48	0.32	0.16	0.16	0.31	2.22	3.63	4.25	2.67	3.23	3.69	3.69	4.55	4.40	4.8

Actual seats

Year	45	50	51	55	59	64	66	70	74F	74O	79	83	87	92	97	01	05
Cons	215	298	321	345	365	303	253	322	296	276	339	397	375	336	165	166	198
Lab	395	315	295	277	258	317	363	288	302	319	268	209	229	271	418	412	355
Lib	12	9	6	6	6	9	12	6	14	13	11	23	22	20	46	52	62
Other	18	3	3	2	1	13	2	14	23	27	17	21	24	24	30	29	31

The relationship between seats and parties

Wikipedia entry on the cube 'law'
Forecasting Seats from Votes in British General Elections, Paul F. Whiteley
Party Size Baselines Imposed by Institutional Constraints, Rein Taagepera
The Number of Parties: New Evidence from Local Elections, Kenneth Benoit (pdf)

KEY:
Blue: Conservative (includes associates, where appropriate)
Red: Labour (includes Labour independents)
Orange: Lib / Alliance / LibDem
Gray: Others

The links on the dates are to more detailed information for that year.

Party share of the votes and seats in UK General Elections since 1945