According to research by Labour Initiative on Co-operation (Linc), alliances between the two parties have been forged on 41 local authorities. At yesterday's Liberal Democrat conference, some delegates said the figure was nearer to 50.
Cuts in spending and a gradual erosion of local government have driven the two parties into pacts to defeat the Conservatives. Linc, a pressure group funded by the Joseph Rowntree Trust, has identified 11 county councils - including Hampshire, Essex, Cambridgeshire, Kent and Berkshire - where otherwise hung or minority councils have been transformed by alliances.
Similarly, 28 district councils, one London borough - Barnet - and North West Somerset Unitary Authority are controlled, or at least spared political paralysis, by Lib-Lab pacts or informal agreements.
"We examined 33 policy documents, including the 1992 election manifestos, and we found surprisingly few differences," said Pete Ruhemann, director of Linc and deputy leader of the Labour group on Berkshire County Council, where Labour and Liberal Democrat members formed an alliance in 1992. "That seems to be why such alliances locally are possible and growing in number. There were times when we found it astonishing that two parties with two such tortuous, and sometimes downright odd, methods of formulating policy could actually come up with almost identical proposals again and again
"There were times when even individual sentences were very, very similar. Politicians at local level found that their similarities far outweigh their differences and they have united to get things done. Of course, we have some serious differences but nothing that can't be overcome. Our policy research suggests that, in the event of a hung parliament, enough agreement could be reached nationally to agree the contents of the first Queen's Speech."
Locally, he argues that much has been achieved. There is less name- calling and less confrontation. Committees have been divided evenly and, where one party has the chairmanship, the other has the deputy's seat.
However, Bob Mowatt, leader of the Liberal Democrats, suggests that the marriage may be one of convenience, built on co-operation, rather than a life-long romance.