BOTH the Liberal Democrats and Conservatives are braced for heavy losses in this week's local elections, with the Coalition partners on track to lose up to 1,500 seats between them.  Labour will be the big winner, with Ed Miliband's party expected to record its biggest share of the vote in council polls for a decade.  The Lib Dems could lose 600 seats on Thursday - a third of all those it holds that will be contested.  a loss on that scale - together with a failure to win the concurrent referendum on changing to the alternative Vote (aV) system - could be enough to prompt discussions about how long Nick Clegg could continue as party leader.  He has already faced criticism from some activists over a U-turn on big increases in university tuition fees and support for Government spending cuts. Chris Huhne, the Lib Dem Climate Change Secretary, is suspected by fellow ministers of being "on manoeuvres" as a possible alternative leader.  In particular, Lib Dem chiefs are braced for losing control of some prized northern councils, including Newcastle upon Tyne and Hull. In Sheffield, where they are currently the largest party, control could pass back to Labour in what would be a significant psychological blow in the city that contains Mr Clegg's parliamentary seat.  However, the Conservatives are also expected to suffer big losses, possibly more than 800. David Cameron's party is defending more than 150 councils and more than 5,000 seats as well as the directly elected mayoralty in Torbay.  "We know we are going to get a kicking and I'm sure the Lib Dems will as well," said one official. "Governing parties always suffer heavy losses in midterm elections. We're currently at a high point in terms of seats."  In 2007, the last time equivalent elections were held, the Tories achieved 40 per cent of the national vote, with Labour on 26 per cent in the dying days of Tony Blair's premiership and the Lib Dems on 24 per cent. Mr Miliband has attempted to play down suggestions that his party will gain 1,000 seats on Thursday, but some polling experts are predicting that they could gain as many as 1,500.  Mr Miliband has campaigned hard in areas such as East anglia and the South West - parts of the country where the party failed to make much of an impact even in the early days of Mr Blair's leadership.  The Labour leader has sought to capitalise on Lib Dem unpopularity in areas where Mr Clegg's party has traditionally been the main opponent of the Conservatives, and used an interview in The Sunday Telegraph last month to burnish his credentials as the candidate for Middle England.  as well as retaking Sheffield, Labour has its sights on Redcar and Cleveland, Bolton, Ipswich and Blackburn, among others, according to research for this newspaper by John Curtice, the professor of politics at Strathclyde University.  Mr Cameron has warned that Labour councillors will repeat what he sees as the tax-and-spend errors of Gordon Brown's government.  "Labour ran our country into the ground. Don't let them do the same to your council," he said last month while campaigning in Darlington. "Put another way - don't let Labour do to your council what they did to our country."  Big overall gains for Labour, however, are likely to be tempered by results of Thursday's elections for the Scottish Parliament, where polls suggest that the Scottish National Party is on course to be well ahead as the largest party with about 60 of the 129 seats.  Such a result would cement alex Salmond's position as First Minister and make a referendum on Scottish independence more likely.  The result of elections to the Welsh assembly are on a knifeedge, with some polls suggesting Labour will just obtain a majority.  Up for grabs on Thursday in England are every seat on 127 shire district councils and 30 unitary councils, as well as a third of the seats on 67 shire district councils, 19 unitary councils and all 36 metropolitan district councils - a total of more than 9,400 seats. There are no local elections in London.  PETER OBORNE: PaGE 24 TOP 25 COUNCILS THaT COULD CHaNGE HaNDS ON MaY 5 Research by John Curtice, Professor of Politics at Strathclyde University Lib Dems No overall control Other Conservative Labour Districts voting Not voting Labour hopes to gain from no overall control 1 Redcar Targeted personally by Ed Miliband who cited Lib Dem broken promises 2 Bolton Just one seat would give Labour control of council it last held in 2002 3 Sheffield Lib Dems are the largest party in Nick Clegg''s backyard - loss to Labour would be a huge blow 4 Ipswich another small gain for Labour would hand it control in a key area for th