A controversial deal with Saudi Arabia catapulted Britain to the top of the world arms export league last year, as UK firms won a record £10bn in orders from overseas, official figures show.

The figure amounts to a third of all worldwide export orders for military equipment, ministers and arms companies reported. An essentially political, government-to-government contract - the sale of 72 Eurofighter/Typhoon aircraft, for £4.4bn, to the Saudis - accounted for Britain's number one position, the figures make clear.

The Ministry of Defence says the terms of the contract - called Salam, Arabic for peace - and the total expenditure involved are confidential. But officials make it clear that when upkeep, spares and training were included, the deal could amount to £20bn spread over many years. The figures last year were also boosted by orders placed by Oman and Trinidad and Tobago for patrol boats.

The companies involved - chiefly BAE Systems and the VT Group - were praised by the trade minister, Digby Jones.

"As demonstrated by this outstanding export performance, the UK has a first-class defence industry, with some of the world's most technologically sophisticated companies," he said.

Traditionally, American arms companies have occupied the top spot in the global arms market, with Britain, Russia and France vying to be the runners-up. Over the past five years the top arms exporters have been the US, with $63bn worth of sales, UK ($53bn), Russia ($33bn), France ($17bn) and Germany and Israel ($9bn each), according to government figures.

Analysts yesterday said that the latest figures reporting Britain's top spot in 2007 should be treated with caution, as they represent orders and not actual deliveries of equipment.

Ron Smith, professor of applied economics at Birkbeck College, University of London, said: "Orders may not be delivered or they may be cancelled."

He warned that statistics about arms sales were unreliable because governments and companies often did not disclose accurate figures for individual contracts.

Roy Isbister, an analyst with the campaigning group Saferworld, said: "Defence sales are notoriously lumpy. This apparent massive increase would seem largely down to the new deal to supply aircraft to Saudi Arabia. On this basis it is highly likely that defence orders will be seen to plummet next year. A clear indication of the UK's status as an arms exporter can only be gained by looking at sales over several years."

Yesterday officials told the Guardian that the value placed on the contracts was commercially sensitive.

The arms trade is notoriously contentious. The MoD, arms fairs, and defence attaches abroad promote British weapons exports, as does Whitehall's defence and security organisation, successor of the defence export sales organisation, Deso. Shortly after Labour came to power in 1997 the government drew up guidelines covering arms sales. They should not be approved, the regulations say, if the sales risk contributing to internal oppression, external aggression, or regional tensions.

According to the latest annual report on weapons-related exports, the government in 2006 approved arms exports to 19 of the 20 countries it identified as "countries of concern" for abusing human rights.

They included Saudi Arabia, Israel, Colombia, China, and Russia. The report also reveals that during 2006 the UK authorised the export of more than 15,000 sniper rifles to countries including Pakistan, Jordan, Turkey and Saudi Arabia, components for military aircraft and tanks for China, and heavy machine guns for Colombia.

They also included the sale of components for combat aircraft, electronic warfare equipment, helicopters, military aircraft cockpit displays, unmanned vehicles and anti-armour missiles for Israel.

Symon Hill, of the Campaign Against the Arms Trade, said: "The majority of arms exported from the UK are sold to oppressive regimes or to countries engaged in conflict. I think that most people in the UK will not be fooled by arms companies which claim to bring great benefits to the UK economy while taking hundreds of millions of pounds of taxpayers' money every year in subsidies."

Government officials say the export guidelines are always taken into account when arms exports are approved.

A report seven years ago by MoD and independent economists, the last published authoritative study on the subject, concluded that in the late 1990s defence exports averaged around £6bn a year and supported about 97,500 jobs, directly or indirectly.

It said that halving arms exports would lead to the loss of about 49,000 jobs but this would be offset by the creation over a five-year period of 67,000 new jobs in non-arms employment.