Oct. 2 (Bloomberg) -- David Cameron has brought his Conservative Party to the brink of an election victory. Now, say former members of Margaret Thatcher’s Cabinet, he must build support for a policy agenda or risk stumbling as prime minister.

The opposition leader, ahead of Prime Minister Gordon Brown in the polls for the last two years, has declined to discuss how he’d keep a lid on military spending or wrest back authority from the European Union. He also won’t say by how much he’d cut Britain’s budget deficit, the highest among the Group of 20 nations, or where the ax will fall.

“You have to have a sufficiently clear view to give people a sense of where you want to go,” said Michael Heseltine, 76, who was appointed environment secretary by Thatcher when she won power in 1979. “When you get into government, you should know precisely what you want to achieve, and not get pushed by your department into their pet schemes.”

As Conservatives prepare for their annual conference, Cameron told the Spectator magazine that he’d begin “saying much more than the government” about his program at the gathering that starts Oct. 5 in Manchester.

His reluctance so far to set out his choices has allowed Conservatives to broaden their appeal, weaning voters away from the Labour Party, which has ruled since 1997. Continuing down that path would leave them beholden to civil servants with their own agenda or without a mandate to make changes, says Patrick Jenkin, 83, social-services secretary in Thatcher’s first cabinet.

‘Years of Work’

“We were able at once to start officials off on tax reforms,” said Jenkin, who also served as a Treasury minister under Edward Heath in the 1970s. “It simply would not have been possible if we had not devoted years of work in preparation. If you put a minister in a department that he has no experience of, he is totally in the hands of his officials.”

It’s not just former ministers demanding more detail from Cameron. Standard & Poor’s says it may downgrade Britain’s AAA credit rating unless the next government sets out a clear path toward reducing the deficit, which will reach 12 percent of gross domestic product in 2010.

Labour ministers are using Cameron’s haziness to supply their own suggestions of how their opponents will make cuts. Brown this week accused the Conservatives of having “no hearts,” suggesting they would fire 3,500 police officers to reduce spending by 10 percent.

So far, saying little about his policies hasn’t hurt Cameron in polls. The Conservatives led Labour by 14 percentage points in a Populus Ltd. survey of 1,506 people finished on Sept. 13. No margin of error was given.

Policy Questions

The inconsistencies in the policies Cameron’s team have discussed so far are starting to add up.

The Conservatives’ main financial commitment is a pledge to increase spending on the state-funded National Health Service and on foreign aid. That, according to the non-partisan Institute for Fiscal Studies, would require a 16 percent spending cut for all other departments over the next six years.

“The important thing is to make it clear now that there are going to have to be cuts, and to avoid making promises of any kind which would lead to an increase in public expenditure and therefore make the matter worse,” said Nigel Lawson, 77, Thatcher’s finance minister from 1983 to 1989.

On defense, Cameron has criticized Brown for not spending enough on Britain’s 9,000 troops in Afghanistan. On Sept. 15, George Osborne, the party’s lawmaker in charge of finance, suggested he’s looking at how to reduce outlays on aircraft carriers, Eurofighter warplanes and a new military transport plane made by London-based BAE Systems Plc and European Aeronautic, Defence & Space Co., which has joint headquarters in Paris and Munich.

European Issue

On the issue of the European Union’s Lisbon Treaty, designed to smooth the governance of the 27-nation bloc, Labour says Cameron’s promise to hold a referendum would leave Britain isolated. Ireland votes today on whether to ratify the treaty.

When faced with questions about policy, Cameron and his team often give answers about the tactics they’re using to win the election, said Tim Montgomerie, founder of Conservative Intelligence, a London-based research institute focused on the party.

“Eighty percent of the time I ask a policy question, I get a political, tactical answer back,” Montgomerie said. “I wonder whether that’s a tactic or whether that’s in their DNA. What’s going to be uppermost in government, their strategic sense or their tactical one?”

Norman Tebbit, 78, who served in Thatcher’s Cabinet from 1981 to 1987, compares his party’s leader to a figure from the opposite end of the political spectrum.

“We look at David Cameron the way the Americans looked at Barack Obama,” Tebbit said in an interview. “They are both well educated, personable, and slightly trendy but with no experience in having to take decisions under pressure. We know now as much about David as the Americans did about Obama.”

To contact the reporter on this story: Kitty Donaldson in London at kdonaldson1@bloomberg.net; Robert Hutton in London at rhutton1@bloomberg.net

Last Updated: October 1, 2009 19:00 EDT