British Prime Minister David Cameron’s Conservatives have notched up a four-point lead over the opposition Labour Party ahead of a May 7 election, an Ashcroft poll showed yesterday, the party’s largest lead in the polling series in six weeks.

If replicated across the country in the election, the lead would not be enough to give the Conservatives an overall majority, however, and was within the margin of error. A week ago, the same poll had both parties neck-and-neck.

The closeness of the race was underlined by two earlier polls yesterday, one of which had the Conservatives two points ahead while the other had the same lead for Labour.

With no sign yet of a surge in support for either the Conservatives or Labour, polls indicate that a hung parliament is the most likely outcome, potentially handing the role of king maker to the leader of a smaller party, such as the Scottish National Party or Liberal Democrats.

Yesterday’s poll, funded by Michael Ashcroft, a former deputy chairman of the Conservatives, put Cameron’s party on 34 per cent, up one point since last week, and Labour down three on 30 per cent.

Support for the United Kingdom Independence party (Ukip) was unchanged on 13 per cent, while the Liberal Democrats were up one point on 10 per cent. Pollsters have said the Conservatives would need a lead over Labour of 7-9 points to secure an overall majority of 326 seats, while Labour – because of the way constituencies are divided up – would need to be around three points ahead, assuming a uniform swing across the country and no change for the other parties.

Meanwhile the Scottish National Party set out plans for higher public spending yesterday, aiming to reverse five years of austerity measures as it goes into a close-run UK election with hopes of winning the power to broker the next British government. The Scottish National Party (SNP), which has rebounded after leading a failed bid for independence last year, is on track to virtually wipe out Labour in Scotland. That could see it become Britain’s third biggest party by seats, but SNP leader Nicola Sturgeon reassured voters outside of Scotland yesterday that she was seeking changes that would benefit the whole of the UK.

In the event of an inconclusive election result, the SNP hopes it will have a decisive say over who forms the next government and has said it will only do a deal with Labour. The SNP plans to free up £3 billion a year for extra spending by scrapping the renewal of Britain’s Trident nuclear deterrent.

The Labour party, however, backs a renewal of Trident.

Labour leader Ed Miliband has ruled out a formal coalition with the SNP, but not a looser vote-by-vote arrangement.