UPDATE 1-UK's Sunak reprimanded by parliament's speaker over budget leaks

(Recasts with Speaker comment, adds details)

By William James

LONDON, March 3 (Reuters) - British finance minister Rishi Sunak was reprimanded by Parliament Speaker Lindsay Hoyle for the leaking of significant announcements worth more than 100 billion pounds ($140 billion) ahead of Wednesday's budget.

Decisions covering more than that amount in Britain's public finances over the next five years were reported anonymously in newspapers or officially announced before Sunak delivered his budget, Reuters analysis showed.

"It is very disappointing that one of the biggest moments in the parliamentary calendar has been undermined by the continuous leaking of significant announcements to the media over several days," Speaker Lindsay Hoyle and his deputy, Eleanor Laing, told Reuters in a joint statement.

"It takes away from the importance of the occasion, which is for everyone to find out the contents of the Budget at the same time - and the principle of announcements of new policy being made to the House first."

Sunak, widely seen as a contender for prime minister in the future, has used the budget to raise his personal profile including the unusual step of publishing his own slick promotional video.

Britain's ministerial code, the government rulebook on conduct and transparency, says that the most important announcements of policy should be made in parliament first.

The government usually makes some spending announcements before budget day but declines to comment or speculate on tax measures in the weeks running up to the statement during a period of self-imposed 'purdah'.

A Treasury official said: "It is usual practice for non-market sensitive policies to be trailed ahead of the budget. A multitude of tax policies are speculated and reported on ahead of budgets. This time has been no different."

BUDGET LEAKS

Ten out of 13 budget measures with a large fiscal impact were reported in advance, according to a Reuters analysis.

Major policies such as the 7 billion pound ($9.8 billion)extension to the government's furlough scheme and a 5 billion pound business grant scheme were announced by the finance ministry before Sunak's speech.

A mortgage guarantee scheme announced on Friday night moved homebuilders' share prices on Monday morning.

Other headline policies such as corporation tax rises and the extension of a tax break on property sales were reported fully or in large part by newspapers using unnamed sources in the run up to their official announcement.

A 'super deduction' tax relief on business investment, support for loss-making businesses, and an extension of support for the hospitality sector had not been reported in advance.

Budget leaks have been treated more seriously in the past.

Back in 1947, then-finance minister Hugh Dalton resigned after revealing some details of his budget announcement to a journalist. In 2013, the Evening Standard newspaper apologised after releasing a front page containing details of the budget before the finance minister had announced them.

Hoyle said that the days of ministers resigning over budget leaks were long gone but that he hoped things would be done better in the future.

Labour lawmaker Chris Bryant told Reuters Sunak had shown "complete contempt" for parliament.

"Privileged access to information about a budget has a value, a currency especially in the markets," he said. "Purdah kept chancellors honest. This opens the door to patronage and insider dealing." ($1 = 0.7166 pounds) (Reporting by William James; editing by Guy Faulconbridge)