UK leaders deliver eye-catching promises as indeterminate vote looms

Polls suggest that Britain's ruling Conservatives and their main opponents, the Labour Party, are neck and neck ahead of their May 7th election. If no party wins a majority, some form of coalition government appears likely.

With four days to go till Britain's election, leaders of the country's main political parties were using the long weekend to make a final push to win over undecided voters before the vote.

Prime Minister David Cameron and his rivals were out Sunday rallying support for the May 7 election, widely expected to be the most unpredictable in decades.

Most opinion polls suggest that the ruling Conservatives and their main opponents, the Labour Party, are neck and neck, each hovering around the 30 to 35 percent mark. If no party wins a majority, some form of coalition government appears likely.

In a speech to activists, Cameron said he is the "only option" for prime minister to avoid a power-sharing deal between Labour and the separatist Scottish National Party — a "calamity for our country," he warned.

Cameron and other party leaders set out their "red lines," or issues they say they wouldn't compromise on should they enter into a governing pact with another party.

The prime minister insisted that if his party wins power again, he wouldn't bargain away their insistence to hold an "in-out" referendum on Britain's European Union membership. Cameron has long said that he wanted Britons to decide whether they want to stay or leave the EU by the end of 2017.

"Come what may, I will not be PM of a government that does not deliver that referendum," he said.

He also appealed to supporters of two smaller parties, the U.K. Independence Party and the Liberal Democrats, to vote Conservative to keep him in office.

Meanwhile, in a bid to show his political commitments, Labour leader and aspiring prime minister Ed Miliband unveiled what election promises his party had carved in stone — literally.

Miliband showed off an eight foot tall limestone monument listing his key manifesto promises, including immigration control and higher living standards for working families.

"We will restore faith in politics by delivering what we promised at this general election," he said.

Cameron mocked the idea, calling it Miliband's "tombstone."