Once the hereditary peerage tipped the Lords massively in favour of the Conservatives. Many of these who enjoyed inherited wealth as well as their seat in Parliament - were members of, or at least very sympathetic to the Conservative Party. [Of course there were also a disproportionate number of Liberals - remnants of the Whigs and their successors - but some hereditary Labour Peers].
The Life Peerages Act 1958 led to a major change over time - as most newcomers were not hereditary peers, but appointed for life.
In 1984/5 There were 405 Conservatives; 123 Labour and 84 Liberal/SDP members (out of a House of 937). By 1994 the balance had shifted even more towards the Tories - 481 peers sat on the Conservative benches (46.3% of the whole House).
The House of Lords Act 1999 removed the right of most hereditaries to sit in the House. Some hereditaries stayed on - as part of the 92 who remained - most after election by their peers. Some were granted life peerages which secured their seats.
The balance shifted immediately - in the 1999/2000 session there were 225 Conservatives; 195 Labour and 61 Liberal Democrat peers. By the end of Labour's period in office, the House consisted of
185 Conservatives (26.2% of the House) 211 Labour (29.9%) and 72 Liberal Democrats (10.2%).
No Government ever had a majority in the House - but Conservative Governments were defeated a lot less frequently (especially when non-aligned hereditary peers were naturally more sympathetic). In 2004/05 - when Labour had a majority over a hundred in the House of Commons - it lost 55.2% of whipped votes in the Lords.
By June 2011 the numbers of Government Peers (now Conservative and Liberal-Democrats) had risen to 39.1% of the House (the Labour Government only enjoyed a membership of 29.9% of the House). Some members of the coalition want the makeup of the House of Lords to mirror the proportions in the House of Commons ((which is course was disproportionate to the votes cast at the election)).
The danger is that a loaded House of Lords will be less likely to carry out its function of being a break on a Government. The Commons already resembles a rubber stamp. Would it be good for British democracy if the House of Lords became one too?
