LONDON (Reuters) - Britain's opposition Labour Party has taken the lead over Prime Minister David Cameron's Conservatives, according to four opinion polls less than a month before the May 7 election, with one survey showing a Labour lead of six percentage points.
Neither Cameron's Conservatives nor Ed Miliband's Labour Party is forecast to win an overall majority in Britain's 650-seat parliament after losing support to once fringe parties such as the Scottish National Party and the UK Independence Party.
An online Panelbase poll published Thursday put Labour up 4 points on 37 percent, the Conservatives down 2 points on 31 percent, UKIP down one point on 16 percent and the Liberal Democrats up one point on 8 percent.
A different online survey by polling firm Survation and conducted for the Daily Mirror newspaper gave Labour a four percentage-point lead over the Conservatives, the biggest Labour lead in a Survation poll since February.
The Survation poll also showed Miliband had overtaken Cameron in terms of net personal approval ratings, the first time Miliband had outpolled Cameron since Survation began asking voters about personal approval ratings in January.
The poll put support for Labour on 35 percent, up from 33 percent since the firm's last poll on April 3, while the Conservatives dipped 1 percentage point to 31 percent.
Support for the anti-EU United Kingdom Independence Party fell 3 percentage points to 15 percent, while the Liberal Democrats were unchanged at 9 percent, and the Scottish nationalists and Greens had 4 percent each, according to Survation.
Opinion polls indicate the Scottish nationalists are on course to win 35-50 of the 59 Westminster seats in Scotland, up from six in 2010, giving them a potential kingmaker position in the Westminster parliament.
The stakes of the election are high: If Cameron wins, he has promised a referendum on European Union membership, while Scottish nationalists have offered to shore up a future Labour minority government in the event of a hung parliament.
The Survation poll surveyed 1,111 people on Wednesday and Thursday. The Panelbase poll surveyed 1,013 people.
A daily YouGov poll for The Sun newspaper published on Thursday put Labour on 35 percent, unchanged from the day before, and the Conservatives on 34 percent, up one percentage point, The Sun said.
A TNS poll put Labour up one on 33 percent, the Conservatives down three points on 30 percent, UKIP up three on 19 percent and the Liberal Democrats unchanged on 8 percent.
Miliband announced on Wednesday that he wanted to scrap tax rules that allow wealthy individuals to legally reduce the amount of tax they pay on money earned overseas.
The Survation poll found 59 percent of respondents supported the idea.
Editing by Kate Holton and Guy Faulconbridge