LONDON - Billionaire John Caudwell, one of the governing Conservative Party's biggest donors before Britain's last national election in 2019, says he no longer wants to back a party that he feels wasted 14 years in power.

But he's not quite ready to donate to Labour.

With a general election due early next month, Caudwell, who made nearly 1.5 billion pounds ($1.9 billion) in 2006 when he sold his mobile phone retailer Phones 4u, still feels he doesn't know enough about the centre-left opposition party's plans.

With the race on to raise campaign funding after Prime Minister Rishi Sunak shocked politicians and big business by calling an early election on July 4, both the Conservatives and Labour are redoubling efforts to court donors.

Labour's leader, Keir Starmer, a former public prosecutor, has charted a centrist course since he took over in 2020, moving the party away from a leftist agenda that saw it lose heavily at the previous election. Polls now suggest that Labour will sweep to victory in July.

But some wealthy donors, like Caudwell, are remaining on the sidelines, unconvinced the party has demonstrated it has the policy solutions to revive Britain's flagging economic growth, modernise its infrastructure and protect public services from attrition.

"Keir Starmer's Labour Party is untested ... and that's a risk," Caudwell said at his marble-floored mansion in London's luxurious Mayfair district. "I'd like to see more concrete stuff from Keir and the potential cabinet, in terms of what's going to happen when they get in power."

"What we do know is the Tories have not done us very well over the last 14 years," Cauldwell told Reuters in an interview, referring to the governing Conservatives. "We just don't know whether Labour would do better."

That's a sentiment shared by many voters. A survey by pollster YouGov in April showed that 50% of respondents were unclear what Labour under Starmer stands for.

Labour did not respond to a request for comment for this story.

Traditionally, the left-leaning party received the bulk of its funding from Britain's union movement.

According to a Reuters' analysis of data from Britain's electoral commission, Starmer has received the second-highest level of private donations for the Labour Party in a single election cycle - behind Labour's term in power in 2005-2010 under former prime ministers Tony Blair and Gordon Brown.

The party has collected about 24 million pounds ($30.6 million) in private donations since 2020, according to Reuters' analysis of data running to April.

Most of that came from wealthy individuals, with around half from three donors: David Sainsbury, a former Labour peer and ex-chairman of the Sainsbury's supermarket chain; his daughter Francesca Perrin; and Gary Lubner, the former CEO of Belron, an international windscreen repair and replacement business.

Sainsbury, Perrin and Lubner did not respond to requests for comment.

More than 9 million pounds have come from new donors, including Lubner. At least eight former Conservative supporters have now switched their allegiance and are now giving money to Labour, with some saying they are persuaded by Labour's promise of a stable environment for business.

Private donations aside, the remainder of Labour's money comes from a mix of trade unions, public funds and other sources - although its financial reliance on the unions is in decline.

Labour received just 23.9 million pounds from trade unions under Starmer, compared with more than 50 million pounds under both his predecessor, the left-wing veteran Jeremy Corbyn, and the prior party leader, Ed Miliband.

The Conservatives are still winning the funding race, taking 104.3 million pounds compared with Labour's 90.2 million in the period since Starmer became leader - something not lost on the opposition party, which regularly sends out email requests for funds, often twice a day.

One Conservative donor, who made a large donation at the last election, said he would not be giving money to the party for this campaign as he didn't expect it to win. The businessman, who requested anonymity so he could speak frankly, also ruled out donating to Labour, citing the risk of higher taxes if they are elected.

Labour has said there will be no rises in income tax or National Insurance social security contributions if it wins power. A Conservative spokesman said the party was "taking bold action to secure a better future for the whole country".

THE PARTY OF BUSINESS?

Ahead of the last election, Cauldwell gave the Conservatives 500,000 pounds because he was convinced that Corbyn "would be absolutely catastrophic for the UK", he said.

Starmer, since becoming Labour leader in 2020, has courted company owners, investors and bankers, aware that the party enjoyed its greatest electoral success in modern times under the pro-business leadership of Blair.

Many businesses, in turn, have clamoured to get access to a team opinion polls say will be the next British government.

Last year's business forum at Labour's annual conference in October had 200 attendees, with more than 180 on the waiting list. The previous one attracted just 130 guests, according to a Labour official.

But four business leaders interviewed for this article said they still have misgivings over whether Starmer, a former public prosecutor, can administer the policies needed to attract investment and spur economic growth in Britain.

For Caudwell, that would mean offering tax breaks to green companies developing cutting-edge environmental technologies that could turn Britain into a leader in the sector - something he doubts whether Labour could do, politically.

Labour, traditionally seen as the party of tax and spend, scaled back a target to invest 28 billion pounds a year in green industries if it wins the election because of what Starmer called the deteriorating economic outlook.

Instead, the party would ramp up investment over time. It plans to adopt a tax break for business known as "full expensing" introduced by the Conservatives last year that allows companies to deduct 100% of the cost of qualifying plant and machinery from their taxable profits.

Caudwell said he would wait to see the Labour manifesto, where the party will set out its agenda for government, to see "if it's truly a party that I can support". Labour expects the manifesto to be published next week. The Conservatives are also expected to publish their manifesto soon.

"I'm still sitting on the fence," Caudwell said.

But if Labour did do more to make Britain more attractive economically, the 71-year-old businessman said he would be happy to donate.

Caudwell proposes attracting green technology companies to Britain by offering a corporation tax holiday stretching to as much as 10 years. In meetings, the Labour leader showed interest in his ideas, even if he was not yet willing to bite, Caudwell said.

"When he wins the election - as I'm sure he will - I'll try and get to him again, and try and put these policies forward to him," Caudwell said.

A spokeswoman for Starmer did not respond to a request for comment.

($1 = 0.7833 pounds)

(Reporting by Elizabeth Piper; Editing by Daniel Flynn)